Index: lib/libc/gen/getgrent.c
===================================================================
--- lib/libc/gen/getgrent.c	(revision 364821)
+++ lib/libc/gen/getgrent.c	(working copy)
@@ -332,10 +332,18 @@
 	orig_buf_size = va_arg(ap, size_t);
 	ret_errno = va_arg(ap, int *);
 
-	if (orig_buf_size <
-	    buffer_size - sizeof(struct group) - sizeof(char *)) {
+	if (orig_buf_size + sizeof(struct group) + sizeof(char *) <
+	    buffer_size)
+	{
 		*ret_errno = ERANGE;
 		return (NS_RETURN);
+	} else if (buffer_size < sizeof(struct group) + sizeof(char *)) {
+		/*
+		 * nscd(8) sometimes returns buffer_size=1 for nonexistent
+		 * groups.
+		 */
+		*ret_errno = 0;
+		return (NS_UNAVAIL);
 	}
 
 	memcpy(grp, buffer, sizeof(struct group));