diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index 9c6e5c0..5b5d8d9 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -63,9 +63,9 @@
   let Funky2: func = function('len')
   let Party2: func = funcref('Test_syntax')
 
-  " type becomes list<any>
+  # type becomes list<any>
   let somelist = rand() > 0 ? [1, 2, 3] : ['a', 'b', 'c']
-  " type becomes dict<any>
+  # type becomes dict<any>
   let somedict = rand() > 0 ? #{a: 1, b: 2} : #{a: 'a', b: 'b'}
 
   g:newvar = 'new'
@@ -104,7 +104,7 @@
   call CheckDefFailure(['&notex += 3'], 'E113:')
   call CheckDefFailure(['&ts ..= "xxx"'], 'E1019:')
   call CheckDefFailure(['&path += 3'], 'E1013:')
-  " test freeing ISN_STOREOPT
+  # test freeing ISN_STOREOPT
   call CheckDefFailure(['&ts = 3', 'let asdf'], 'E1022:')
   &ts = 8
 
@@ -131,7 +131,7 @@
 
 def Test_assignment_default()
 
-  " Test default values.
+  # Test default values.
   let thebool: bool
   assert_equal(v:false, thebool)
 
diff --git a/src/version.c b/src/version.c
index f7dfb38..c0c2e98 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    583,
+/**/
     582,
 /**/
     581,
diff --git a/src/vim9compile.c b/src/vim9compile.c
index 1ccf1a7..4137c56 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -5772,7 +5772,7 @@
      */
     for (;;)
     {
-	int	is_ex_command;
+	int	is_ex_command = FALSE;
 
 	// Bail out on the first error to avoid a flood of errors and report
 	// the right line number when inside try/catch.
@@ -5791,6 +5791,7 @@
 	{
 	    line = next_line_from_context(&cctx);
 	    if (cctx.ctx_lnum >= ufunc->uf_lines.ga_len)
+		// beyond the last line
 		break;
 	}
 	emsg_before = called_emsg;
@@ -5800,35 +5801,53 @@
 	ea.cmdlinep = &line;
 	ea.cmd = skipwhite(line);
 
-	// "}" ends a block scope
-	if (*ea.cmd == '}')
+	// Some things can be recognized by the first character.
+	switch (*ea.cmd)
 	{
-	    scopetype_T stype = cctx.ctx_scope == NULL
-					 ? NO_SCOPE : cctx.ctx_scope->se_type;
+	    case '#':
+		// "#" starts a comment, but not "#{".
+		if (ea.cmd[1] != '{')
+		{
+		    line = (char_u *)"";
+		    continue;
+		}
+		break;
 
-	    if (stype == BLOCK_SCOPE)
-	    {
-		compile_endblock(&cctx);
-		line = ea.cmd;
-	    }
-	    else
-	    {
-		emsg(_("E1025: using } outside of a block scope"));
-		goto erret;
-	    }
-	    if (line != NULL)
-		line = skipwhite(ea.cmd + 1);
-	    continue;
-	}
+	    case '}':
+		{
+		    // "}" ends a block scope
+		    scopetype_T stype = cctx.ctx_scope == NULL
+					  ? NO_SCOPE : cctx.ctx_scope->se_type;
 
-	// "{" starts a block scope
-	// "{'a': 1}->func() is something else
-	if (*ea.cmd == '{' && ends_excmd(*skipwhite(ea.cmd + 1)))
-	{
-	    line = compile_block(ea.cmd, &cctx);
-	    continue;
+		    if (stype == BLOCK_SCOPE)
+		    {
+			compile_endblock(&cctx);
+			line = ea.cmd;
+		    }
+		    else
+		    {
+			emsg(_("E1025: using } outside of a block scope"));
+			goto erret;
+		    }
+		    if (line != NULL)
+			line = skipwhite(ea.cmd + 1);
+		    continue;
+		}
+
+	    case '{':
+		// "{" starts a block scope
+		// "{'a': 1}->func() is something else
+		if (ends_excmd(*skipwhite(ea.cmd + 1)))
+		{
+		    line = compile_block(ea.cmd, &cctx);
+		    continue;
+		}
+		break;
+
+	    case ':':
+		is_ex_command = TRUE;
+		break;
 	}
-	is_ex_command = *ea.cmd == ':';
 
 	/*
 	 * COMMAND MODIFIERS