diff -up a/extensions/auth/nsAuthSambaNTLM.cpp.old b/extensions/auth/nsAuthSambaNTLM.cpp
--- a/extensions/auth/nsAuthSambaNTLM.cpp.old	2014-11-25 12:23:22.000000000 +0100
+++ b/extensions/auth/nsAuthSambaNTLM.cpp	2014-12-23 15:26:36.606674625 +0100
@@ -161,7 +161,7 @@
   const char* username = PR_GetEnv("USER");
   if (!username) return NS_ERROR_FAILURE;
 
-  const char* const args[] = {"ntlm_auth",
+  const char* const args[] = {"/usr/bin/ntlm_auth",
                               "--helper-protocol",
                               "ntlmssp-client-1",
                               "--use-cached-creds",