diff --git a/src/ex_cmds.c b/src/ex_cmds.c
index 614d41d..d8c5a12 100644
--- a/src/ex_cmds.c
+++ b/src/ex_cmds.c
@@ -3643,6 +3643,17 @@
     return p;
 }
 
+    static int
+check_regexp_delim(int c)
+{
+    if (isalpha(c))
+    {
+	emsg(_("E146: Regular expressions can't be delimited by letters"));
+	return FAIL;
+    }
+    return OK;
+}
+
 /*
  * Perform a substitution from line eap->line1 to line eap->line2 using the
  * command pointed to by eap->arg which should be of the form:
@@ -3705,11 +3716,9 @@
 		&& vim_strchr((char_u *)"0123456789cegriIp|\"", *cmd) == NULL)
     {
 				// don't accept alphanumeric for separator
-	if (isalpha(*cmd))
-	{
-	    emsg(_("E146: Regular expressions can't be delimited by letters"));
+	if (check_regexp_delim(*cmd) == FAIL)
 	    return;
-	}
+
 	/*
 	 * undocumented vi feature:
 	 *  "\/sub/" and "\?sub?" use last used search pattern (almost like
@@ -4909,6 +4918,10 @@
 	emsg(_("E148: Regular expression missing from global"));
 	return;
     }
+    else if (check_regexp_delim(*cmd) == FAIL)
+    {
+	return;
+    }
     else
     {
 	delim = *cmd;		// get the delimiter