diff --git a/src/vim9compile.c b/src/vim9compile.c
index 0db5162..1edf48c 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -2290,6 +2290,7 @@
 {
     char_u  *p = *arg;
     char_u  *whitep = *arg;
+    int	    must_end = FALSE;
 
     for (;;)
     {
@@ -2300,6 +2301,11 @@
 	    *arg = p + 1;
 	    return OK;
 	}
+	if (must_end)
+	{
+	    semsg(_(e_missing_comma_before_argument_str), p);
+	    return FAIL;
+	}
 
 	if (compile_expr0(&p, cctx) == FAIL)
 	    return FAIL;
@@ -2316,6 +2322,8 @@
 	    if (*p != NUL && !VIM_ISWHITE(*p))
 		semsg(_(e_white_space_required_after_str), ",");
 	}
+	else
+	    must_end = TRUE;
 	whitep = p;
 	p = skipwhite(p);
     }