diff --git a/runtime/doc/vim9.txt b/runtime/doc/vim9.txt
index 88c35de..dd2d510 100644
--- a/runtime/doc/vim9.txt
+++ b/runtime/doc/vim9.txt
@@ -58,6 +58,15 @@
 
 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE
 
+Comments starting with # ~
+
+In Vim script comments normally start with double quote.  That can also be the
+start of a string, thus in many places it cannot be used.  In Vim9 script a
+comment can also start with #.  Normally this is a command to list text with
+numbers, but you can also use `:number` for that. >
+	let count = 0  # number of occurences of Ni!
+
+
 Vim9 functions ~
 
 `:def` has no extra arguments like `:function` does: "range", "abort", "dict"
@@ -241,6 +250,9 @@
 	let var =234	" Error!
 There must be white space before and after the "=": >
 	let var = 234	" OK
+White space must also be put before the # that starts a comment: >
+	let var = 234# Error!
+	let var = 234 # OK
 
 White space is required around most operators.
 
diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index 1cc231d..047e368 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -4764,6 +4764,9 @@
     int
 ends_excmd(int c)
 {
+    if (c == '#')
+	// TODO: should check for preceding white space
+	return in_vim9script();
     return (c == NUL || c == '|' || c == '"' || c == '\n');
 }
 
diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index c98acc9..f0b0ad0 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
@@ -569,6 +569,14 @@
   return arg1 .. arg2 .. join(rest, '-')
 enddef
 
+def MultiLineComment(
+    arg1: string, # comment
+    arg2 = 1234, # comment
+    ...rest: list<string> # comment
+      ): string # comment
+  return arg1 .. arg2 .. join(rest, '-')
+enddef
+
 def Test_multiline()
   assert_equal('text1234', MultiLine('text'))
   assert_equal('text777', MultiLine('text', 777))
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index 3a08344..c3e3f22 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -983,10 +983,17 @@
       } " comment
   assert_equal({'one': 1, 'two': 2, 'three': 3}, mydict)
   mydict = #{
-      one: 1,  " comment
-      two:
-           2,
-      three: 3  " comment
+      one: 1,  # comment
+      two:     # comment
+           2,  # comment
+      three: 3 # comment
+      }
+  assert_equal(#{one: 1, two: 2, three: 3}, mydict)
+  mydict = #{
+      one: 1, 
+      two: 
+           2, 
+      three: 3 
       }
   assert_equal(#{one: 1, two: 2, three: 3}, mydict)
 
diff --git a/src/userfunc.c b/src/userfunc.c
index 98e1ec5..95483e2 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -154,6 +154,7 @@
     int		c;
     int		any_default = FALSE;
     char_u	*expr;
+    char_u	*whitep = arg;
 
     if (newargs != NULL)
 	ga_init2(newargs, (int)sizeof(char_u *), 3);
@@ -170,7 +171,8 @@
      */
     while (*p != endchar)
     {
-	if (eap != NULL && *p == NUL && eap->getline != NULL)
+	while (eap != NULL && eap->getline != NULL
+			 && (*p == NUL || (VIM_ISWHITE(*whitep) && *p == '#')))
 	{
 	    char_u *theline;
 
@@ -180,6 +182,7 @@
 		break;
 	    vim_free(*line_to_free);
 	    *line_to_free = theline;
+	    whitep = (char_u *)" ";
 	    p = skipwhite(theline);
 	}
 
@@ -228,6 +231,7 @@
 		// find the end of the expression (doesn't evaluate it)
 		any_default = TRUE;
 		p = skipwhite(p) + 1;
+		whitep = p;
 		p = skipwhite(p);
 		expr = p;
 		if (eval1(&p, &rettv, FALSE) != FAIL)
@@ -264,6 +268,7 @@
 	    else
 		mustend = TRUE;
 	}
+	whitep = p;
 	p = skipwhite(p);
     }
 
@@ -2595,7 +2600,8 @@
     // Makes 'exe "func Test()\n...\nendfunc"' work.
     if (*p == '\n')
 	line_arg = p + 1;
-    else if (*p != NUL && *p != '"' && !eap->skip && !did_emsg)
+    else if (*p != NUL && *p != '"' && !(eap->cmdidx == CMD_def && *p == '#')
+						    && !eap->skip && !did_emsg)
 	emsg(_(e_trailing));
 
     /*
diff --git a/src/version.c b/src/version.c
index 35f8df8..d4250e5 100644
--- a/src/version.c
+++ b/src/version.c
@@ -739,6 +739,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    567,
+/**/
     566,
 /**/
     565,
diff --git a/src/vim9compile.c b/src/vim9compile.c
index 8a4684d..666db15 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -2070,13 +2070,23 @@
 }
 
 /*
+ * Return TRUE if "p" points at a "#" but not at "#{".
+ */
+    static int
+comment_start(char_u *p)
+{
+    return p[0] == '#' && p[1] != '{';
+}
+
+/*
  * If "*arg" is at the end of the line, advance to the next line.
+ * Also when "whitep" points to white space and "*arg" is on a "#".
  * Return FAIL if beyond the last line, "*arg" is unmodified then.
  */
     static int
-may_get_next_line(char_u **arg, cctx_T *cctx)
+may_get_next_line(char_u *whitep, char_u **arg, cctx_T *cctx)
 {
-    if (**arg == NUL)
+    if (**arg == NUL || (VIM_ISWHITE(*whitep) && comment_start(*arg)))
     {
 	char_u *next = next_line_from_context(cctx);
 
@@ -2321,15 +2331,17 @@
     static int
 compile_arguments(char_u **arg, cctx_T *cctx, int *argcount)
 {
-    char_u *p = *arg;
+    char_u  *p = *arg;
+    char_u  *whitep = *arg;
 
     for (;;)
     {
-	if (*p == NUL)
+	while (*p == NUL || (VIM_ISWHITE(*whitep) && comment_start(p)))
 	{
 	    p = next_line_from_context(cctx);
 	    if (p == NULL)
-		break;
+		goto failret;
+	    whitep = (char_u *)" ";
 	    p = skipwhite(p);
 	}
 	if (*p == ')')
@@ -2353,9 +2365,10 @@
 	    if (*p != NUL && !VIM_ISWHITE(*p))
 		semsg(_(e_white_after), ",");
 	}
+	whitep = p;
 	p = skipwhite(p);
     }
-
+failret:
     emsg(_(e_missing_close));
     return FAIL;
 }
@@ -2589,11 +2602,12 @@
 compile_list(char_u **arg, cctx_T *cctx)
 {
     char_u	*p = skipwhite(*arg + 1);
+    char_u	*whitep = *arg + 1;
     int		count = 0;
 
     for (;;)
     {
-	if (*p == NUL)
+	while (*p == NUL || (VIM_ISWHITE(*whitep) && comment_start(p)))
 	{
 	    p = next_line_from_context(cctx);
 	    if (p == NULL)
@@ -2601,6 +2615,7 @@
 		semsg(_(e_list_end), *arg);
 		return FAIL;
 	    }
+	    whitep = (char_u *)" ";
 	    p = skipwhite(p);
 	}
 	if (*p == ']')
@@ -2616,6 +2631,7 @@
 	++count;
 	if (*p == ',')
 	    ++p;
+	whitep = p;
 	p = skipwhite(p);
     }
     *arg = p;
@@ -2713,6 +2729,8 @@
     int		count = 0;
     dict_T	*d = dict_alloc();
     dictitem_T	*item;
+    char_u	*whitep = *arg;
+    char_u	*p;
 
     if (d == NULL)
 	return FAIL;
@@ -2721,11 +2739,13 @@
     {
 	char_u *key = NULL;
 
-	if (**arg == NUL || (literal && **arg == '"'))
+	while (**arg == NUL || (literal && **arg == '"')
+			      || (VIM_ISWHITE(*whitep) && comment_start(*arg)))
 	{
 	    *arg = next_line_from_context(cctx);
 	    if (*arg == NULL)
 		goto failret;
+	    whitep = (char_u *)" ";
 	    *arg = skipwhite(*arg);
 	}
 
@@ -2734,17 +2754,17 @@
 
 	if (literal)
 	{
-	    char_u *p = to_name_end(*arg, !literal);
+	    char_u *end = to_name_end(*arg, !literal);
 
-	    if (p == *arg)
+	    if (end == *arg)
 	    {
 		semsg(_("E1014: Invalid key: %s"), *arg);
 		return FAIL;
 	    }
-	    key = vim_strnsave(*arg, p - *arg);
+	    key = vim_strnsave(*arg, end - *arg);
 	    if (generate_PUSHS(cctx, key) == FAIL)
 		return FAIL;
-	    *arg = p;
+	    *arg = end;
 	}
 	else
 	{
@@ -2784,12 +2804,14 @@
 	    return FAIL;
 	}
 
+	whitep = *arg + 1;
 	*arg = skipwhite(*arg + 1);
-	if (**arg == NUL)
+	while (**arg == NUL || (VIM_ISWHITE(*whitep) && comment_start(*arg)))
 	{
 	    *arg = next_line_from_context(cctx);
 	    if (*arg == NULL)
 		goto failret;
+	    whitep = (char_u *)" ";
 	    *arg = skipwhite(*arg);
 	}
 
@@ -2797,12 +2819,16 @@
 	    return FAIL;
 	++count;
 
-	if (**arg == NUL || *skipwhite(*arg) == '"')
+	whitep = *arg;
+	p = skipwhite(*arg);
+	while (*p == NUL || (VIM_ISWHITE(*whitep) && comment_start(p)))
 	{
 	    *arg = next_line_from_context(cctx);
 	    if (*arg == NULL)
 		goto failret;
+	    whitep = (char_u *)" ";
 	    *arg = skipwhite(*arg);
+	    p = *arg;
 	}
 	if (**arg == '}')
 	    break;
@@ -2811,13 +2837,15 @@
 	    semsg(_(e_missing_dict_comma), *arg);
 	    goto failret;
 	}
+	whitep = *arg + 1;
 	*arg = skipwhite(*arg + 1);
     }
 
     *arg = *arg + 1;
 
     // Allow for following comment, after at least one space.
-    if (VIM_ISWHITE(**arg) && *skipwhite(*arg) == '"')
+    p = skipwhite(*arg);
+    if (VIM_ISWHITE(**arg) && (*p == '"' || comment_start(p)))
 	*arg += STRLEN(*arg);
 
     dict_unref(d);
@@ -3422,7 +3450,7 @@
 	    return FAIL;
 	}
 	*arg = skipwhite(op + 1);
-	if (may_get_next_line(arg, cctx) == FAIL)
+	if (may_get_next_line(op + 1, arg, cctx) == FAIL)
 	    return FAIL;
 
 	// get the second variable
@@ -3470,7 +3498,7 @@
 	}
 
 	*arg = skipwhite(op + oplen);
-	if (may_get_next_line(arg, cctx) == FAIL)
+	if (may_get_next_line(op + oplen, arg, cctx) == FAIL)
 	    return FAIL;
 
 	// get the second variable
@@ -3608,7 +3636,7 @@
 
 	// get the second variable
 	*arg = skipwhite(p + len);
-	if (may_get_next_line(arg, cctx) == FAIL)
+	if (may_get_next_line(p + len, arg, cctx) == FAIL)
 	    return FAIL;
 
 	if (compile_expr5(arg, cctx) == FAIL)
@@ -3658,7 +3686,7 @@
 
 	    // eval the next expression
 	    *arg = skipwhite(p + 2);
-	    if (may_get_next_line(arg, cctx) == FAIL)
+	    if (may_get_next_line(p + 2, arg, cctx) == FAIL)
 		return FAIL;
 
 	    if ((opchar == '|' ? compile_expr3(arg, cctx)
@@ -3771,7 +3799,7 @@
 
 	// evaluate the second expression; any type is accepted
 	*arg = skipwhite(p + 1);
-	if (may_get_next_line(arg, cctx) == FAIL)
+	if (may_get_next_line(p + 1, arg, cctx) == FAIL)
 	    return FAIL;
 
 	if (compile_expr1(arg, cctx) == FAIL)
@@ -3803,7 +3831,7 @@
 
 	// evaluate the third expression
 	*arg = skipwhite(p + 1);
-	if (may_get_next_line(arg, cctx) == FAIL)
+	if (may_get_next_line(p + 1, arg, cctx) == FAIL)
 	    return FAIL;
 
 	if (compile_expr1(arg, cctx) == FAIL)