diff --git a/sshpubk.c b/sshpubk.c
index 78a35ee7..dd06ebd5 100644
--- a/sshpubk.c
+++ b/sshpubk.c
@@ -835,7 +835,8 @@ struct ssh2_userkey *ssh2_load_userkey(const Filename *filename,
     sfree(public_blob);
     sfree(private_blob);
     sfree(encryption);
-    *errorstr = NULL;
+    if (errorstr)
+	*errorstr = NULL;
     return ret;
 
     /*