diff --git a/auth.c b/auth.c
index f5b7aa0..985eee4 100644
--- a/auth.c
+++ b/auth.c
@@ -12,6 +12,7 @@
 #include <stdlib.h>
 #include <alloca.h>
 #include <string.h>
+#include <ctype.h>
 #include "ldap.h"
 #include "auth.h"
 #include <libowfat/str.h>
@@ -31,7 +32,7 @@ int check_password(const char* fromdb,struct string* plaintext) {
     if (str_equal(md5,fromdb+5))
       return 1;
   }
-  if (plaintext->l<100 && (str_start(fromdb,"$1$") || strlen(fromdb)==13)) {
+  if (plaintext->l<100 && ((fromdb[0]=='$' && fromdb[2]=='$' && isdigit(fromdb[1])) || strlen(fromdb)==13)) {
     char* c=alloca(plaintext->l+1);
     byte_copy(c,plaintext->l,plaintext->s);
     c[plaintext->l]=0;