diff --git a/src/eval.c b/src/eval.c
index 8a6539e..ffc7122 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -3536,7 +3536,7 @@
 			if (ufunc->uf_ret_type->tt_type == VAR_VOID)
 			    ufunc->uf_ret_type = &t_unknown;
 			if (compile_def_function(ufunc,
-					 FALSE, PROFILING(ufunc), NULL) == FAIL)
+				     FALSE, COMPILE_TYPE(ufunc), NULL) == FAIL)
 			{
 			    clear_tv(rettv);
 			    ret = FAIL;
diff --git a/src/proto/vim9compile.pro b/src/proto/vim9compile.pro
index 39624ae..881dddc 100644
--- a/src/proto/vim9compile.pro
+++ b/src/proto/vim9compile.pro
@@ -3,7 +3,7 @@
 int check_compare_types(exprtype_T type, typval_T *tv1, typval_T *tv2);
 int use_typecheck(type_T *actual, type_T *expected);
 int need_type(type_T *actual, type_T *expected, int offset, int arg_idx, cctx_T *cctx, int silent, int actual_is_const);
-int func_needs_compiling(ufunc_T *ufunc, int profile);
+int func_needs_compiling(ufunc_T *ufunc, compiletype_T compile_type);
 int get_script_item_idx(int sid, char_u *name, int check_writable, cctx_T *cctx);
 imported_T *find_imported(char_u *name, size_t len, cctx_T *cctx);
 imported_T *find_imported_in_script(char_u *name, size_t len, int sid);
@@ -17,7 +17,7 @@
 int assignment_len(char_u *p, int *heredoc);
 void vim9_declare_error(char_u *name);
 int check_vim9_unlet(char_u *name);
-int compile_def_function(ufunc_T *ufunc, int check_return_type, int profiling, cctx_T *outer_cctx);
+int compile_def_function(ufunc_T *ufunc, int check_return_type, compiletype_T compile_type, cctx_T *outer_cctx);
 void set_function_type(ufunc_T *ufunc);
 void delete_instr(isn_T *isn);
 void unlink_def_function(ufunc_T *ufunc);
diff --git a/src/testdir/test_debugger.vim b/src/testdir/test_debugger.vim
index 029b9db..ed4bacc 100644
--- a/src/testdir/test_debugger.vim
+++ b/src/testdir/test_debugger.vim
@@ -884,19 +884,20 @@
                 \ ':debug call GlobalFunction()',
                 \ ['cmd: call GlobalFunction()'])
 
-  " FIXME: Vim9 lines are not debugged!
-  call RunDbgCmd(buf, 'step', ['line 1: source Xtest2.vim'])
+  call RunDbgCmd(buf, 'step', ['line 1:   CallAFunction()'])
 
-  " But they do appear in the backtrace
+  " FIXME: not quite right
   call RunDbgCmd(buf, 'backtrace', [
         \ '\V>backtrace',
-        \ '\V  2 function GlobalFunction[1]',
-        \ '\V  1 <SNR>\.\*_CallAFunction[1]',
-        \ '\V->0 <SNR>\.\*_SourceAnotherFile',
-        \ '\Vline 1: source Xtest2.vim'],
+        \ '\V->0 function GlobalFunction',
+        \ '\Vline 1:   CallAFunction()',
+        \ ],
         \ #{match: 'pattern'})
 
-
+  call RunDbgCmd(buf, 'step', ['line 1:   SourceAnotherFile()'])
+  call RunDbgCmd(buf, 'step', ['line 1:   source Xtest2.vim'])
+  " FIXME: repeated line
+  call RunDbgCmd(buf, 'step', ['line 1: source Xtest2.vim'])
   call RunDbgCmd(buf, 'step', ['line 1: vim9script'])
   call RunDbgCmd(buf, 'step', ['line 3: def DoAThing(): number'])
   call RunDbgCmd(buf, 'step', ['line 9: export def File2Function()'])
@@ -913,7 +914,7 @@
         \ #{match: 'pattern'})
 
   " Don't step into compiled functions...
-  call RunDbgCmd(buf, 'step', ['line 15: End of sourced file'])
+  call RunDbgCmd(buf, 'next', ['line 15: End of sourced file'])
   call RunDbgCmd(buf, 'backtrace', [
         \ '\V>backtrace',
         \ '\V  3 function GlobalFunction[1]',
@@ -923,7 +924,6 @@
         \ '\Vline 15: End of sourced file'],
         \ #{match: 'pattern'})
 
-
   call StopVimInTerminal(buf)
   call delete('Xtest1.vim')
   call delete('Xtest2.vim')
@@ -1116,6 +1116,7 @@
         \ [ 'E121: Undefined variable: s:file1_var' ] )
   call RunDbgCmd(buf, 'echo s:file2_var', [ 'file2' ] )
 
+  call RunDbgCmd(buf, 'cont')
   call StopVimInTerminal(buf)
   call delete('Xtest1.vim')
   call delete('Xtest2.vim')
diff --git a/src/testdir/test_vim9_disassemble.vim b/src/testdir/test_vim9_disassemble.vim
index 965399b..e1ed675 100644
--- a/src/testdir/test_vim9_disassemble.vim
+++ b/src/testdir/test_vim9_disassemble.vim
@@ -2153,7 +2153,7 @@
   if !has('profile')
     MissingFeature 'profile'
   endif
-  var res = execute('disass! s:Profiled')
+  var res = execute('disass profile s:Profiled')
   assert_match('<SNR>\d*_Profiled\_s*' ..
         'echo "profiled"\_s*' ..
         '\d PROFILE START line 1\_s*' ..
@@ -2168,6 +2168,20 @@
         res)
 enddef
 
+def Test_debugged()
+  var res = execute('disass debug s:Profiled')
+  assert_match('<SNR>\d*_Profiled\_s*' ..
+        'echo "profiled"\_s*' ..
+        '\d DEBUG line 1\_s*' ..
+        '\d PUSHS "profiled"\_s*' ..
+        '\d ECHO 1\_s*' ..
+        'return "done"\_s*' ..
+        '\d DEBUG line 2\_s*' ..
+        '\d PUSHS "done"\_s*' ..
+        '\d RETURN\_s*',
+        res)
+enddef
+
 def s:EchoMessages()
   echohl ErrorMsg | echom v:exception | echohl NONE
 enddef
diff --git a/src/userfunc.c b/src/userfunc.c
index f610c02..56b7df3 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -4395,7 +4395,7 @@
 		    && ufunc->uf_def_status == UF_TO_BE_COMPILED
 		    && (ufunc->uf_flags & FC_DEAD) == 0)
 	    {
-		(void)compile_def_function(ufunc, FALSE, FALSE, NULL);
+		(void)compile_def_function(ufunc, FALSE, CT_NONE, NULL);
 
 		if (func_hashtab.ht_changed != changed)
 		{
diff --git a/src/version.c b/src/version.c
index 7f459c2..ad399ce 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2985,
+/**/
     2984,
 /**/
     2983,
diff --git a/src/vim.h b/src/vim.h
index e1e68f9..784fa3a 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -1794,10 +1794,17 @@
 typedef int proftime_T;	    // dummy for function prototypes
 #endif
 
+// Type of compilation passed to compile_def_function()
+typedef enum {
+    CT_NONE,	    // use df_instr
+    CT_PROFILE,	    // use df_instr_prof
+    CT_DEBUG	    // use df_instr_debug, overrules CT_PROFILE
+} compiletype_T;
+
 #ifdef FEAT_PROFILE
-# define PROFILING(ufunc) (do_profiling == PROF_YES && (ufunc)->uf_profiling)
+# define COMPILE_TYPE(ufunc) (debug_break_level > 0 ? CT_DEBUG : do_profiling == PROF_YES && (ufunc)->uf_profiling ? CT_PROFILE : CT_NONE)
 #else
-# define PROFILING(ufunc) FALSE
+# define COMPILE_TYPE(ufunc) debug_break_level > 0 ? CT_DEBUG : CT_NONE
 #endif
 
 /*
diff --git a/src/vim9.h b/src/vim9.h
index d4d3b7d..f434602 100644
--- a/src/vim9.h
+++ b/src/vim9.h
@@ -168,6 +168,8 @@
     ISN_PROF_START, // start a line for profiling
     ISN_PROF_END,   // end a line for profiling
 
+    ISN_DEBUG,	    // check for debug breakpoint
+
     ISN_UNPACK,	    // unpack list into items, uses isn_arg.unpack
     ISN_SHUFFLE,    // move item on stack up or down
     ISN_DROP,	    // pop stack and discard value
@@ -453,6 +455,8 @@
     isn_T	*df_instr_prof;	     // like "df_instr" with profiling
     int		df_instr_prof_count; // size of "df_instr_prof"
 #endif
+    isn_T	*df_instr_debug;      // like "df_instr" with debugging
+    int		df_instr_debug_count; // size of "df_instr_debug"
 
     int		df_varcount;	    // number of local variables
     int		df_has_closure;	    // one if a closure was created
diff --git a/src/vim9compile.c b/src/vim9compile.c
index 47847af..7c01906 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -174,7 +174,7 @@
     char_u	*ctx_line_start;    // start of current line or NULL
     garray_T	ctx_instr;	    // generated instructions
 
-    int		ctx_profiling;	    // when TRUE generate ISN_PROF_START
+    compiletype_T ctx_compile_type;
 
     garray_T	ctx_locals;	    // currently visible local variables
     int		ctx_locals_count;   // total number of local variables
@@ -1857,7 +1857,7 @@
  * "profile" indicates profiling is to be done.
  */
     int
-func_needs_compiling(ufunc_T *ufunc, int profile UNUSED)
+func_needs_compiling(ufunc_T *ufunc, compiletype_T compile_type)
 {
     switch (ufunc->uf_def_status)
     {
@@ -1866,15 +1866,18 @@
 
 	case UF_COMPILED:
 	{
-#ifdef FEAT_PROFILE
 	    dfunc_T *dfunc = ((dfunc_T *)def_functions.ga_data)
 							 + ufunc->uf_dfunc_idx;
 
-	    return profile ? dfunc->df_instr_prof == NULL
-			   : dfunc->df_instr == NULL;
-#else
-	    break;
-#endif
+	    switch (compile_type)
+	    {
+		case CT_NONE:
+		    return dfunc->df_instr == NULL;
+		case CT_PROFILE:
+		    return dfunc->df_instr_prof == NULL;
+		case CT_DEBUG:
+		    return dfunc->df_instr_debug == NULL;
+	    }
 	}
 
 	case UF_NOT_COMPILED:
@@ -1945,9 +1948,9 @@
 		return FAIL;
 	    }
 	}
-	if (func_needs_compiling(ufunc, PROFILING(ufunc))
+	if (func_needs_compiling(ufunc, COMPILE_TYPE(ufunc))
 		&& compile_def_function(ufunc, ufunc->uf_ret_type == NULL,
-					       PROFILING(ufunc), NULL) == FAIL)
+					    COMPILE_TYPE(ufunc), NULL) == FAIL)
 	    return FAIL;
     }
     if (ufunc->uf_def_status == UF_COMPILE_ERROR)
@@ -2313,14 +2316,28 @@
     garray_T	*instr = &cctx->ctx_instr;
     int		idx = instr->ga_len;
 
-    if (cctx->ctx_has_cmdmod && ((isn_T *)instr->ga_data)[idx - 1]
+    while (idx > 0)
+    {
+	if (cctx->ctx_has_cmdmod && ((isn_T *)instr->ga_data)[idx - 1]
 						       .isn_type == ISN_CMDMOD)
-	--idx;
+	{
+	    --idx;
+	    continue;
+	}
 #ifdef FEAT_PROFILE
-    if (cctx->ctx_profiling && ((isn_T *)instr->ga_data)[idx - 1]
-						   .isn_type == ISN_PROF_START)
-	--idx;
+	if (((isn_T *)instr->ga_data)[idx - 1].isn_type == ISN_PROF_START)
+	{
+	    --idx;
+	    continue;
+	}
 #endif
+	if (((isn_T *)instr->ga_data)[idx - 1].isn_type == ISN_DEBUG)
+	{
+	    --idx;
+	    continue;
+	}
+	break;
+    }
     return idx;
 }
 
@@ -2328,7 +2345,7 @@
     static void
 may_generate_prof_end(cctx_T *cctx, int prof_lnum)
 {
-    if (cctx->ctx_profiling && prof_lnum >= 0)
+    if (cctx->ctx_compile_type == CT_PROFILE && prof_lnum >= 0)
 	generate_instr(cctx, ISN_PROF_END);
 }
 #endif
@@ -2972,8 +2989,8 @@
 	return FAIL;
 
     // Need to compile any default values to get the argument types.
-    if (func_needs_compiling(ufunc, PROFILING(ufunc))
-	    && compile_def_function(ufunc, TRUE, PROFILING(ufunc), NULL)
+    if (func_needs_compiling(ufunc, COMPILE_TYPE(ufunc))
+	    && compile_def_function(ufunc, TRUE, COMPILE_TYPE(ufunc), NULL)
 								       == FAIL)
 	return FAIL;
     return generate_PUSHFUNC(cctx, ufunc->uf_name, ufunc->uf_func_type);
@@ -3570,7 +3587,7 @@
     // compile_return().
     if (ufunc->uf_ret_type->tt_type == VAR_VOID)
 	ufunc->uf_ret_type = &t_unknown;
-    compile_def_function(ufunc, FALSE, PROFILING(ufunc), cctx);
+    compile_def_function(ufunc, FALSE, COMPILE_TYPE(ufunc), cctx);
 
     // evalarg.eval_tofree_cmdline may have a copy of the last line and "*arg"
     // points into it.  Point to the original line to avoid a dangling pointer.
@@ -5566,8 +5583,8 @@
 	}
     }
 
-    if (func_needs_compiling(ufunc, PROFILING(ufunc))
-	    && compile_def_function(ufunc, TRUE, PROFILING(ufunc), cctx)
+    if (func_needs_compiling(ufunc, COMPILE_TYPE(ufunc))
+	    && compile_def_function(ufunc, TRUE, COMPILE_TYPE(ufunc), cctx)
 								       == FAIL)
     {
 	func_ptr_unref(ufunc);
@@ -7376,7 +7393,7 @@
 	scope->se_u.se_if.is_if_label = -1;
 
 #ifdef FEAT_PROFILE
-    if (cctx->ctx_profiling && cctx->ctx_skip == SKIP_YES
+    if (cctx->ctx_compile_type == CT_PROFILE && cctx->ctx_skip == SKIP_YES
 						      && skip_save != SKIP_YES)
     {
 	// generated a profile start, need to generate a profile end, since it
@@ -7457,13 +7474,19 @@
     {
 	cctx->ctx_skip = SKIP_UNKNOWN;
 #ifdef FEAT_PROFILE
-	if (cctx->ctx_profiling)
+	if (cctx->ctx_compile_type == CT_PROFILE)
 	{
 	    // the previous block was skipped, need to profile this line
 	    generate_instr(cctx, ISN_PROF_START);
 	    instr_count = instr->ga_len;
 	}
 #endif
+	if (cctx->ctx_compile_type == CT_DEBUG)
+	{
+	    // the previous block was skipped, may want to debug this line
+	    generate_instr(cctx, ISN_DEBUG);
+	    instr_count = instr->ga_len;
+	}
     }
     if (compile_expr1(&p, cctx, &ppconst) == FAIL)
     {
@@ -7531,12 +7554,13 @@
     scope->se_u.se_if.is_seen_else = TRUE;
 
 #ifdef FEAT_PROFILE
-    if (cctx->ctx_profiling)
+    if (cctx->ctx_compile_type == CT_PROFILE)
     {
 	if (cctx->ctx_skip == SKIP_NOT
 		&& ((isn_T *)instr->ga_data)[instr->ga_len - 1]
 						   .isn_type == ISN_PROF_START)
-	    // the previous block was executed, do not count "else" for profiling
+	    // the previous block was executed, do not count "else" for
+	    // profiling
 	    --instr->ga_len;
 	if (cctx->ctx_skip == SKIP_YES && !scope->se_u.se_if.is_seen_skip_not)
 	{
@@ -7612,7 +7636,7 @@
 #ifdef FEAT_PROFILE
     // even when skipping we count the endif as executed, unless the block it's
     // in is skipped
-    if (cctx->ctx_profiling && cctx->ctx_skip == SKIP_YES
+    if (cctx->ctx_compile_type == CT_PROFILE && cctx->ctx_skip == SKIP_YES
 					    && scope->se_skip_save != SKIP_YES)
     {
 	cctx->ctx_skip = SKIP_NOT;
@@ -8183,7 +8207,8 @@
     {
 #ifdef FEAT_PROFILE
 	// the profile-start should be after the jump
-	if (cctx->ctx_profiling && ((isn_T *)instr->ga_data)[instr->ga_len - 1]
+	if (cctx->ctx_compile_type == CT_PROFILE
+		&& ((isn_T *)instr->ga_data)[instr->ga_len - 1]
 						   .isn_type == ISN_PROF_START)
 	    --instr->ga_len;
 #endif
@@ -8203,7 +8228,7 @@
 	    isn->isn_arg.jump.jump_where = instr->ga_len;
 	}
 #ifdef FEAT_PROFILE
-	if (cctx->ctx_profiling)
+	if (cctx->ctx_compile_type == CT_PROFILE)
 	{
 	    // a "throw" that jumps here needs to be counted
 	    generate_instr(cctx, ISN_PROF_END);
@@ -8211,6 +8236,8 @@
 	    generate_instr(cctx, ISN_PROF_START);
 	}
 #endif
+	if (cctx->ctx_compile_type == CT_DEBUG)
+	    generate_instr(cctx, ISN_DEBUG);
     }
 
     p = skipwhite(arg);
@@ -8298,7 +8325,8 @@
 
     this_instr = instr->ga_len;
 #ifdef FEAT_PROFILE
-    if (cctx->ctx_profiling && ((isn_T *)instr->ga_data)[instr->ga_len - 1]
+    if (cctx->ctx_compile_type == CT_PROFILE
+	    && ((isn_T *)instr->ga_data)[instr->ga_len - 1]
 						   .isn_type == ISN_PROF_START)
 	// jump to the profile start of the "finally"
 	--this_instr;
@@ -8367,7 +8395,8 @@
 	}
 
 #ifdef FEAT_PROFILE
-	if (cctx->ctx_profiling && ((isn_T *)instr->ga_data)[instr->ga_len - 1]
+	if (cctx->ctx_compile_type == CT_PROFILE
+		&& ((isn_T *)instr->ga_data)[instr->ga_len - 1]
 						.isn_type == ISN_PROF_START)
 	    // move the profile start after "endtry" so that it's not counted when
 	    // the exception is rethrown.
@@ -8399,7 +8428,7 @@
 				   && generate_instr(cctx, ISN_ENDTRY) == NULL)
 	    return NULL;
 #ifdef FEAT_PROFILE
-	if (cctx->ctx_profiling)
+	if (cctx->ctx_compile_type == CT_PROFILE)
 	    generate_instr(cctx, ISN_PROF_START);
 #endif
     }
@@ -8965,10 +8994,10 @@
  */
     int
 compile_def_function(
-	ufunc_T	    *ufunc,
-	int	    check_return_type,
-	int	    profiling UNUSED,
-	cctx_T	    *outer_cctx)
+	ufunc_T		*ufunc,
+	int		check_return_type,
+	compiletype_T   compile_type,
+	cctx_T		*outer_cctx)
 {
     char_u	*line = NULL;
     char_u	*line_to_free = NULL;
@@ -8987,6 +9016,7 @@
 #ifdef FEAT_PROFILE
     int		prof_lnum = -1;
 #endif
+    int		debug_lnum = -1;
 
     // When using a function that was compiled before: Free old instructions.
     // The index is reused.  Otherwise add a new entry in "def_functions".
@@ -9007,9 +9037,7 @@
 
     CLEAR_FIELD(cctx);
 
-#ifdef FEAT_PROFILE
-    cctx.ctx_profiling = profiling;
-#endif
+    cctx.ctx_compile_type = compile_type;
     cctx.ctx_ufunc = ufunc;
     cctx.ctx_lnum = -1;
     cctx.ctx_outer = outer_cctx;
@@ -9159,8 +9187,8 @@
 	}
 
 #ifdef FEAT_PROFILE
-	if (cctx.ctx_profiling && cctx.ctx_lnum != prof_lnum &&
-						     cctx.ctx_skip != SKIP_YES)
+	if (cctx.ctx_compile_type == CT_PROFILE && cctx.ctx_lnum != prof_lnum
+						  && cctx.ctx_skip != SKIP_YES)
 	{
 	    may_generate_prof_end(&cctx, prof_lnum);
 
@@ -9168,6 +9196,12 @@
 	    generate_instr(&cctx, ISN_PROF_START);
 	}
 #endif
+	if (cctx.ctx_compile_type == CT_DEBUG && cctx.ctx_lnum != debug_lnum
+						  && cctx.ctx_skip != SKIP_YES)
+	{
+	    debug_lnum = cctx.ctx_lnum;
+	    generate_instr(&cctx, ISN_DEBUG);
+	}
 
 	// Some things can be recognized by the first character.
 	switch (*ea.cmd)
@@ -9617,13 +9651,19 @@
 	dfunc->df_deleted = FALSE;
 	dfunc->df_script_seq = current_sctx.sc_seq;
 #ifdef FEAT_PROFILE
-	if (cctx.ctx_profiling)
+	if (cctx.ctx_compile_type == CT_PROFILE)
 	{
 	    dfunc->df_instr_prof = instr->ga_data;
 	    dfunc->df_instr_prof_count = instr->ga_len;
 	}
 	else
 #endif
+	if (cctx.ctx_compile_type == CT_DEBUG)
+	{
+	    dfunc->df_instr_debug = instr->ga_data;
+	    dfunc->df_instr_debug_count = instr->ga_len;
+	}
+	else
 	{
 	    dfunc->df_instr = instr->ga_data;
 	    dfunc->df_instr_count = instr->ga_len;
@@ -9919,6 +9959,7 @@
 	case ISN_COMPARESTRING:
 	case ISN_CONCAT:
 	case ISN_COND2BOOL:
+	case ISN_DEBUG:
 	case ISN_DROP:
 	case ISN_ECHO:
 	case ISN_ECHOERR:
@@ -9927,6 +9968,7 @@
 	case ISN_EXECCONCAT:
 	case ISN_EXECUTE:
 	case ISN_FINALLY:
+	case ISN_FINISH:
 	case ISN_FOR:
 	case ISN_GETITEM:
 	case ISN_JUMP:
@@ -9949,7 +9991,6 @@
 	case ISN_NEWLIST:
 	case ISN_OPANY:
 	case ISN_OPFLOAT:
-	case ISN_FINISH:
 	case ISN_OPNR:
 	case ISN_PCALL:
 	case ISN_PCALL_END:
diff --git a/src/vim9execute.c b/src/vim9execute.c
index 767dcea..c1e40a6 100644
--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -204,8 +204,8 @@
 	// Profiling might be enabled/disabled along the way.  This should not
 	// fail, since the function was compiled before and toggling profiling
 	// doesn't change any errors.
-	if (func_needs_compiling(ufunc, PROFILING(ufunc))
-		&& compile_def_function(ufunc, FALSE, PROFILING(ufunc), NULL)
+	if (func_needs_compiling(ufunc, COMPILE_TYPE(ufunc))
+		&& compile_def_function(ufunc, FALSE, COMPILE_TYPE(ufunc), NULL)
 								       == FAIL)
 	    return FAIL;
     }
@@ -264,6 +264,7 @@
     // If depth of calling is getting too high, don't execute the function.
     if (funcdepth_increment() == FAIL)
 	return FAIL;
+    ++ex_nesting_level;
 
     // Only make a copy of funclocal if it contains something to restore.
     if (ectx->ec_funclocal.floc_restore_cmdmod)
@@ -647,6 +648,7 @@
 	ectx->ec_stack.ga_len = top;
 
     funcdepth_decrement();
+    --ex_nesting_level;
     return OK;
 }
 
@@ -737,13 +739,15 @@
     int		idx;
     int		did_emsg_before = did_emsg;
 #ifdef FEAT_PROFILE
-    int		profiling = do_profiling == PROF_YES && ufunc->uf_profiling;
+    compiletype_T compile_type = do_profiling == PROF_YES
+				 && ufunc->uf_profiling ? CT_PROFILE : CT_NONE;
 #else
-# define profiling FALSE
+# define compile_type CT_NONE
 #endif
 
-    if (func_needs_compiling(ufunc, profiling)
-		&& compile_def_function(ufunc, FALSE, profiling, NULL) == FAIL)
+    if (func_needs_compiling(ufunc, compile_type)
+		&& compile_def_function(ufunc, FALSE, compile_type, NULL)
+								       == FAIL)
 	return FAIL;
     if (ufunc->uf_def_status == UF_COMPILED)
     {
@@ -4099,6 +4103,22 @@
 		}
 		break;
 
+	    case ISN_DEBUG:
+		if (ex_nesting_level <= debug_break_level)
+		{
+		    char_u	*line;
+		    ufunc_T	*ufunc = (((dfunc_T *)def_functions.ga_data)
+					       + ectx->ec_dfunc_idx)->df_ufunc;
+
+		    SOURCING_LNUM = iptr->isn_lnum;
+		    line = ((char_u **)ufunc->uf_lines.ga_data)[
+							   iptr->isn_lnum - 1];
+		    if (line == NULL)
+			line = (char_u *)"[empty]";
+		    do_debug(line);
+		}
+		break;
+
 	    case ISN_SHUFFLE:
 		{
 		    typval_T	tmp_tv;
@@ -4258,6 +4278,7 @@
     int		save_emsg_silent_def = emsg_silent_def;
     int		save_did_emsg_def = did_emsg_def;
     int		orig_funcdepth;
+    int		orig_nesting_level = ex_nesting_level;
 
 // Get pointer to item in the stack.
 #undef STACK_TV
@@ -4273,8 +4294,8 @@
 
     if (ufunc->uf_def_status == UF_NOT_COMPILED
 	    || ufunc->uf_def_status == UF_COMPILE_ERROR
-	    || (func_needs_compiling(ufunc, PROFILING(ufunc))
-		&& compile_def_function(ufunc, FALSE, PROFILING(ufunc), NULL)
+	    || (func_needs_compiling(ufunc, COMPILE_TYPE(ufunc))
+		&& compile_def_function(ufunc, FALSE, COMPILE_TYPE(ufunc), NULL)
 								      == FAIL))
     {
 	if (did_emsg_cumul + did_emsg == did_emsg_before)
@@ -4310,6 +4331,7 @@
     ga_init2(&ectx.ec_trystack, sizeof(trycmd_T), 10);
     ga_init2(&ectx.ec_funcrefs, sizeof(partial_T *), 10);
     ectx.ec_did_emsg_before = did_emsg_before;
+    ++ex_nesting_level;
 
     idx = argc - ufunc->uf_args.ga_len;
     if (idx > 0 && ufunc->uf_va_name == NULL)
@@ -4553,6 +4575,7 @@
     // Free all local variables, but not arguments.
     for (idx = 0; idx < ectx.ec_stack.ga_len; ++idx)
 	clear_tv(STACK_TV(idx));
+    ex_nesting_level = orig_nesting_level;
 
     vim_free(ectx.ec_stack.ga_data);
     vim_free(ectx.ec_trystack.ga_data);
@@ -5315,13 +5338,18 @@
 	    case ISN_CMDMOD_REV: smsg("%s%4d CMDMOD_REV", pfx, current); break;
 
 	    case ISN_PROF_START:
-		 smsg("%s%4d PROFILE START line %d", pfx, current, iptr->isn_lnum);
+		 smsg("%s%4d PROFILE START line %d", pfx, current,
+							       iptr->isn_lnum);
 		 break;
 
 	    case ISN_PROF_END:
 		smsg("%s%4d PROFILE END", pfx, current);
 		break;
 
+	    case ISN_DEBUG:
+		smsg("%s%4d DEBUG line %d", pfx, current, iptr->isn_lnum);
+		break;
+
 	    case ISN_UNPACK: smsg("%s%4d UNPACK %d%s", pfx, current,
 			iptr->isn_arg.unpack.unp_count,
 			iptr->isn_arg.unpack.unp_semicolon ? " semicolon" : "");
@@ -5358,6 +5386,18 @@
     isn_T	*instr;
     int		instr_count;
     int		is_global = FALSE;
+    compiletype_T compile_type = CT_NONE;
+
+    if (STRNCMP(arg, "profile", 7) == 0)
+    {
+	compile_type = CT_PROFILE;
+	arg = skipwhite(arg + 7);
+    }
+    else if (STRNCMP(arg, "debug", 5) == 0)
+    {
+	compile_type = CT_DEBUG;
+	arg = skipwhite(arg + 5);
+    }
 
     if (STRNCMP(arg, "<lambda>", 8) == 0)
     {
@@ -5389,8 +5429,8 @@
 	semsg(_(e_cannot_find_function_str), eap->arg);
 	return;
     }
-    if (func_needs_compiling(ufunc, eap->forceit)
-	    && compile_def_function(ufunc, FALSE, eap->forceit, NULL) == FAIL)
+    if (func_needs_compiling(ufunc, compile_type)
+	    && compile_def_function(ufunc, FALSE, compile_type, NULL) == FAIL)
 	return;
     if (ufunc->uf_def_status != UF_COMPILED)
     {
@@ -5403,14 +5443,24 @@
 	msg((char *)ufunc->uf_name);
 
     dfunc = ((dfunc_T *)def_functions.ga_data) + ufunc->uf_dfunc_idx;
+    switch (compile_type)
+    {
+	case CT_PROFILE:
 #ifdef FEAT_PROFILE
-    instr = eap->forceit ? dfunc->df_instr_prof : dfunc->df_instr;
-    instr_count = eap->forceit ? dfunc->df_instr_prof_count
-						       : dfunc->df_instr_count;
-#else
-    instr = dfunc->df_instr;
-    instr_count = dfunc->df_instr_count;
+	    instr = dfunc->df_instr_prof;
+	    instr_count = dfunc->df_instr_prof_count;
+	    break;
 #endif
+	    // FALLTHROUGH
+	case CT_NONE:
+	    instr = dfunc->df_instr;
+	    instr_count = dfunc->df_instr_count;
+	    break;
+	case CT_DEBUG:
+	    instr = dfunc->df_instr_debug;
+	    instr_count = dfunc->df_instr_debug_count;
+	    break;
+    }
 
     list_instructions("", instr, instr_count, ufunc);
 }
diff --git a/src/vim9type.c b/src/vim9type.c
index 4dec1e7..f3718e4 100644
--- a/src/vim9type.c
+++ b/src/vim9type.c
@@ -349,7 +349,7 @@
 	    // May need to get the argument types from default values by
 	    // compiling the function.
 	    if (ufunc->uf_def_status == UF_TO_BE_COMPILED
-			    && compile_def_function(ufunc, TRUE, FALSE, NULL)
+			    && compile_def_function(ufunc, TRUE, CT_NONE, NULL)
 								       == FAIL)
 		return NULL;
 	    if (ufunc->uf_func_type == NULL)