diff --git a/src/evalfunc.c b/src/evalfunc.c
index 08f8847..7f6cbac 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -3056,8 +3056,8 @@
     int
 check_internal_func(int idx, int argcount)
 {
-    int	    res;
-    char    *name;
+    funcerror_T	    res;
+    char	    *name;
 
     if (argcount < global_functions[idx].f_min_argc)
 	res = FCERR_TOOFEW;
@@ -3074,7 +3074,7 @@
     return -1;
 }
 
-    int
+    funcerror_T
 call_internal_func(
 	char_u	    *name,
 	int	    argcount,
@@ -3107,7 +3107,7 @@
 /*
  * Invoke a method for base->method().
  */
-    int
+    funcerror_T
 call_internal_method(
 	char_u	    *name,
 	int	    argcount,
diff --git a/src/if_lua.c b/src/if_lua.c
index 45f233f..6559550 100644
--- a/src/if_lua.c
+++ b/src/if_lua.c
@@ -2776,11 +2776,11 @@
     if (lua_pcall(funcstate->L, luaargcount, 1, 0))
     {
 	luaV_emsg(funcstate->L);
-	return FCERR_OTHER;
+	return (int)FCERR_OTHER;
     }
 
     luaV_checktypval(funcstate->L, -1, rettv, "get return value");
-    return FCERR_NONE;
+    return (int)FCERR_NONE;
 }
 
 /*
diff --git a/src/proto/evalfunc.pro b/src/proto/evalfunc.pro
index 78998ff..a720b64 100644
--- a/src/proto/evalfunc.pro
+++ b/src/proto/evalfunc.pro
@@ -10,9 +10,9 @@
 type_T *internal_func_ret_type(int idx, int argcount, type2_T *argtypes, type_T **decl_type, garray_T *type_gap);
 int internal_func_is_map(int idx);
 int check_internal_func(int idx, int argcount);
-int call_internal_func(char_u *name, int argcount, typval_T *argvars, typval_T *rettv);
+funcerror_T call_internal_func(char_u *name, int argcount, typval_T *argvars, typval_T *rettv);
 void call_internal_func_by_idx(int idx, typval_T *argvars, typval_T *rettv);
-int call_internal_method(char_u *name, int argcount, typval_T *argvars, typval_T *rettv, typval_T *basetv);
+funcerror_T call_internal_method(char_u *name, int argcount, typval_T *argvars, typval_T *rettv, typval_T *basetv);
 int non_zero_arg(typval_T *argvars);
 buf_T *get_buf_arg(typval_T *arg);
 win_T *get_optional_window(typval_T *argvars, int idx);
diff --git a/src/proto/userfunc.pro b/src/proto/userfunc.pro
index 94b53f6..cda0389 100644
--- a/src/proto/userfunc.pro
+++ b/src/proto/userfunc.pro
@@ -9,7 +9,7 @@
 void emsg_funcname(char *ermsg, char_u *name);
 int get_func_arguments(char_u **arg, evalarg_T *evalarg, int partial_argc, typval_T *argvars, int *argcount);
 int get_func_tv(char_u *name, int len, typval_T *rettv, char_u **arg, evalarg_T *evalarg, funcexe_T *funcexe);
-char_u *fname_trans_sid(char_u *name, char_u *fname_buf, char_u **tofree, int *error);
+char_u *fname_trans_sid(char_u *name, char_u *fname_buf, char_u **tofree, funcerror_T *error);
 void func_name_with_sid(char_u *name, int sid, char_u *buffer);
 ufunc_T *find_func_even_dead(char_u *name, int flags);
 ufunc_T *find_func(char_u *name, int is_global);
@@ -24,8 +24,8 @@
 void funcdepth_restore(int depth);
 funccall_T *create_funccal(ufunc_T *fp, typval_T *rettv);
 void remove_funccal(void);
-int check_user_func_argcount(ufunc_T *fp, int argcount);
-int call_user_func_check(ufunc_T *fp, int argcount, typval_T *argvars, typval_T *rettv, funcexe_T *funcexe, dict_T *selfdict);
+funcerror_T check_user_func_argcount(ufunc_T *fp, int argcount);
+funcerror_T call_user_func_check(ufunc_T *fp, int argcount, typval_T *argvars, typval_T *rettv, funcexe_T *funcexe, dict_T *selfdict);
 void save_funccal(funccal_entry_T *entry);
 void restore_funccal(void);
 funccall_T *get_current_funccal(void);
@@ -37,7 +37,7 @@
 int get_callback_depth(void);
 int call_callback(callback_T *callback, int len, typval_T *rettv, int argcount, typval_T *argvars);
 varnumber_T call_callback_retnr(callback_T *callback, int argcount, typval_T *argvars);
-void user_func_error(int error, char_u *name, int found_var);
+void user_func_error(funcerror_T error, char_u *name, int found_var);
 int call_func(char_u *funcname, int len, typval_T *rettv, int argcount_in, typval_T *argvars_in, funcexe_T *funcexe);
 int call_simple_func(char_u *funcname, int len, typval_T *rettv);
 char_u *printable_func_name(ufunc_T *fp);
diff --git a/src/testdir/test_vim9_class.vim b/src/testdir/test_vim9_class.vim
index e73b31c..2cd3bdd 100644
--- a/src/testdir/test_vim9_class.vim
+++ b/src/testdir/test_vim9_class.vim
@@ -195,6 +195,26 @@
       echo db[state.value]
   END
   v9.CheckScriptFailure(lines, 'E1360:')
+
+  lines =<< trim END
+      vim9script
+
+      class Background
+        this.background = 'dark'
+      endclass
+
+      class Colorscheme
+        this._bg: Background
+
+        def GetBackground(): string
+          return this._bg.background
+        enddef
+      endclass
+
+      var bg: Background           # UNINITIALIZED
+      echo Colorscheme.new(bg).GetBackground()
+  END
+  v9.CheckScriptFailure(lines, 'E1012: Type mismatch; expected object<Background> but got object<Unknown>')
 enddef
 
 def Test_class_member_initializer()
diff --git a/src/userfunc.c b/src/userfunc.c
index 1009cd7..d5dd369 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -1979,7 +1979,11 @@
  * and set "tofree".
  */
     char_u *
-fname_trans_sid(char_u *name, char_u *fname_buf, char_u **tofree, int *error)
+fname_trans_sid(
+	char_u	    *name,
+	char_u	    *fname_buf,
+	char_u	    **tofree,
+	funcerror_T *error)
 {
     int		llen;
     char_u	*fname;
@@ -2716,7 +2720,7 @@
 /*
  * Call a user function.
  */
-    static void
+    static funcerror_T
 call_user_func(
     ufunc_T	*fp,		// pointer to function
     int		argcount,	// nr of args
@@ -2731,6 +2735,7 @@
     int		save_sticky_cmdmod_flags = sticky_cmdmod_flags;
     funccall_T	*fc;
     int		save_did_emsg;
+    funcerror_T retval = FCERR_NONE;
     int		default_arg_err = FALSE;
     dictitem_T	*v;
     int		fixvar_idx = 0;	// index in fc_fixvar[]
@@ -2755,14 +2760,14 @@
     {
 	rettv->v_type = VAR_NUMBER;
 	rettv->vval.v_number = -1;
-	return;
+	return FCERR_FAILED;
     }
 
     line_breakcheck();		// check for CTRL-C hit
 
     fc = create_funccal(fp, rettv);
     if (fc == NULL)
-	return;
+	return FCERR_OTHER;
     fc->fc_level = ex_nesting_level;
     // Check if this function has a breakpoint.
     fc->fc_breakpoint = dbg_find_breakpoint(FALSE, fp->uf_name, (linenr_T)0);
@@ -2781,8 +2786,9 @@
 	    profile_may_start_func(&profile_info, fp, caller);
 #endif
 	sticky_cmdmod_flags = 0;
-	call_def_function(fp, argcount, argvars, 0,
-			   funcexe->fe_partial, funcexe->fe_object, fc, rettv);
+	if (call_def_function(fp, argcount, argvars, 0,
+		   funcexe->fe_partial, funcexe->fe_object, fc, rettv) == FAIL)
+	    retval = FCERR_FAILED;
 	funcdepth_decrement();
 #ifdef FEAT_PROFILE
 	if (do_profiling == PROF_YES && (fp->uf_profiling
@@ -2791,7 +2797,7 @@
 #endif
 	remove_funccal();
 	sticky_cmdmod_flags = save_sticky_cmdmod_flags;
-	return;
+	return retval;
     }
 
     islambda = fp->uf_flags & FC_LAMBDA;
@@ -3024,7 +3030,10 @@
     did_emsg = FALSE;
 
     if (default_arg_err && (fp->uf_flags & FC_ABORT))
+    {
 	did_emsg = TRUE;
+	retval = FCERR_FAILED;
+    }
     else if (islambda)
     {
 	char_u *p = *(char_u **)fp->uf_lines.ga_data + 7;
@@ -3051,6 +3060,7 @@
 	clear_tv(rettv);
 	rettv->v_type = VAR_NUMBER;
 	rettv->vval.v_number = -1;
+	retval = FCERR_FAILED;
     }
 
 #ifdef FEAT_PROFILE
@@ -3134,13 +3144,15 @@
     for (i = 0; i < tv_to_free_len; ++i)
 	clear_tv(tv_to_free[i]);
     cleanup_function_call(fc);
+
+    return retval;
 }
 
 /*
  * Check the argument count for user function "fp".
  * Return FCERR_UNKNOWN if OK, FCERR_TOOFEW or FCERR_TOOMANY otherwise.
  */
-    int
+    funcerror_T
 check_user_func_argcount(ufunc_T *fp, int argcount)
 {
     int regular_args = fp->uf_args.ga_len;
@@ -3155,7 +3167,7 @@
 /*
  * Call a user function after checking the arguments.
  */
-    int
+    funcerror_T
 call_user_func_check(
 	ufunc_T	    *fp,
 	int	    argcount,
@@ -3164,7 +3176,7 @@
 	funcexe_T   *funcexe,
 	dict_T	    *selfdict)
 {
-    int error;
+    funcerror_T error = FCERR_NONE;
 
 #ifdef FEAT_LUA
     if (fp->uf_flags & FC_CFUNC)
@@ -3180,8 +3192,11 @@
     error = check_user_func_argcount(fp, argcount);
     if (error != FCERR_UNKNOWN)
 	return error;
+
     if ((fp->uf_flags & FC_DICT) && selfdict == NULL)
+    {
 	error = FCERR_DICT;
+    }
     else
     {
 	int		did_save_redo = FALSE;
@@ -3199,7 +3214,7 @@
 	    did_save_redo = TRUE;
 	}
 	++fp->uf_calls;
-	call_user_func(fp, argcount, argvars, rettv, funcexe,
+	error = call_user_func(fp, argcount, argvars, rettv, funcexe,
 				   (fp->uf_flags & FC_DICT) ? selfdict : NULL);
 	if (--fp->uf_calls <= 0 && fp->uf_refcount <= 0)
 	    // Function was unreferenced while being used, free it now.
@@ -3207,8 +3222,8 @@
 	if (did_save_redo)
 	    restoreRedobuff(&save_redo);
 	restore_search_patterns();
-	error = FCERR_NONE;
     }
+
     return error;
 }
 
@@ -3542,7 +3557,7 @@
  * Nothing if "error" is FCERR_NONE.
  */
     void
-user_func_error(int error, char_u *name, int found_var)
+user_func_error(funcerror_T error, char_u *name, int found_var)
 {
     switch (error)
     {
@@ -3571,6 +3586,12 @@
 		emsg_funcname(e_calling_dict_function_without_dictionary_str,
 									 name);
 		break;
+	case FCERR_OTHER:
+	case FCERR_FAILED:
+		// assume the error message was already given
+		break;
+	case FCERR_NONE:
+		break;
     }
 }
 
@@ -3591,7 +3612,7 @@
     funcexe_T	*funcexe)	// more arguments
 {
     int		ret = FAIL;
-    int		error = FCERR_NONE;
+    funcerror_T	error = FCERR_NONE;
     int		i;
     ufunc_T	*fp = NULL;
     char_u	fname_buf[FLEN_FIXED + 1];
@@ -3823,7 +3844,7 @@
     typval_T	*rettv)		// return value goes here
 {
     int		ret = FAIL;
-    int		error = FCERR_NONE;
+    funcerror_T	error = FCERR_NONE;
     char_u	fname_buf[FLEN_FIXED + 1];
     char_u	*tofree = NULL;
     char_u	*name;
@@ -5973,8 +5994,7 @@
 	    // we tolerate an unknown function here, it might be defined later
 	    if (ufunc != NULL)
 	    {
-		int error = check_user_func_argcount(ufunc, argcount);
-
+		funcerror_T error = check_user_func_argcount(ufunc, argcount);
 		if (error != FCERR_UNKNOWN)
 		{
 		    user_func_error(error, name, FALSE);
@@ -6449,7 +6469,6 @@
     char_u	*fname;
     ufunc_T	*fp = NULL;
     char_u	fname_buf[FLEN_FIXED + 1];
-    int		error;
     dict_T	*selfdict = selfdict_in;
 
     if (rettv->v_type == VAR_PARTIAL  && rettv->vval.v_partial != NULL
@@ -6470,6 +6489,7 @@
 	else
 	{
 	    char_u	*tofree = NULL;
+	    funcerror_T	error;
 
 	    // Translate "s:func" to the stored function name.
 	    fname = fname_trans_sid(fname, fname_buf, &tofree, &error);
@@ -6881,7 +6901,7 @@
 {
     ufunc_T	*fp = fp_in;
     funccall_T	*fc;
-    int		error = FCERR_NONE;
+    funcerror_T	error = FCERR_NONE;
     char_u	fname_buf[FLEN_FIXED + 1];
     char_u	*tofree = NULL;
     char_u	*fname;
diff --git a/src/version.c b/src/version.c
index d6cee20..20df490 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1320,
+/**/
     1319,
 /**/
     1318,
diff --git a/src/vim.h b/src/vim.h
index 67bb23e..45b5fa9 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -2270,6 +2270,20 @@
     KEYPROTOCOL_FAIL
 } keyprot_T;
 
+// errors for when calling a function
+typedef enum {
+    FCERR_NONE,		// no error
+    FCERR_UNKNOWN,	// unknown function
+    FCERR_TOOMANY,	// too many arguments
+    FCERR_TOOFEW,	// too few arguments
+    FCERR_SCRIPT,	// missing script context
+    FCERR_DICT,		// missing dict
+    FCERR_OTHER,	// another kind of error
+    FCERR_DELETED,	// function was deleted
+    FCERR_NOTMETHOD,	// function cannot be used as a method
+    FCERR_FAILED,	// error while executing the function
+} funcerror_T;
+
 // Flags for assignment functions.
 #define ASSIGN_VAR	0     // ":var" (nothing special)
 #define ASSIGN_FINAL	0x01  // ":final"
@@ -2703,17 +2717,6 @@
 #define DO_NOT_FREE_CNT 99999	// refcount for dict or list that should not
 				// be freed.
 
-// errors for when calling a function
-#define FCERR_UNKNOWN	0
-#define FCERR_TOOMANY	1
-#define FCERR_TOOFEW	2
-#define FCERR_SCRIPT	3
-#define FCERR_DICT	4
-#define FCERR_NONE	5
-#define FCERR_OTHER	6
-#define FCERR_DELETED	7
-#define FCERR_NOTMETHOD	8   // function cannot be used as a method
-
 // fixed buffer length for fname_trans_sid()
 #define FLEN_FIXED 40
 
diff --git a/src/vim9execute.c b/src/vim9execute.c
index 49042a4..4bbed82 100644
--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -1283,7 +1283,7 @@
 {
     typval_T	argvars[MAX_FUNC_ARGS];
     funcexe_T   funcexe;
-    int		error;
+    funcerror_T	error;
     int		idx;
     int		did_emsg_before = did_emsg;
     compiletype_T compile_type = get_compile_type(ufunc);
@@ -1464,10 +1464,10 @@
 	name = tv->vval.v_string;
     if (name != NULL)
     {
-	char_u	fname_buf[FLEN_FIXED + 1];
-	char_u	*tofree = NULL;
-	int	error = FCERR_NONE;
-	char_u	*fname;
+	char_u	    fname_buf[FLEN_FIXED + 1];
+	char_u	    *tofree = NULL;
+	funcerror_T error = FCERR_NONE;
+	char_u	    *fname;
 
 	// May need to translate <SNR>123_ to K_SNR.
 	fname = fname_trans_sid(name, fname_buf, &tofree, &error);
diff --git a/src/vim9type.c b/src/vim9type.c
index 075eb60..c9f72df 100644
--- a/src/vim9type.c
+++ b/src/vim9type.c
@@ -1659,7 +1659,8 @@
 
     if (type->tt_type == VAR_OBJECT || type->tt_type == VAR_CLASS)
     {
-	char_u *class_name = ((class_T *)type->tt_member)->class_name;
+	char_u *class_name = type->tt_member == NULL ? (char_u *)"Unknown"
+				    : ((class_T *)type->tt_member)->class_name;
 	size_t len = STRLEN(name) + STRLEN(class_name) + 3;
 	*tofree = alloc(len);
 	if (*tofree != NULL)