diff --git a/security/manager/ssl/nsNTLMAuthModule.cpp b/security/manager/ssl/nsNTLMAuthModule.cpp
index d574950..17d7050 100644
--- a/security/manager/ssl/nsNTLMAuthModule.cpp
+++ b/security/manager/ssl/nsNTLMAuthModule.cpp
@@ -591,6 +591,8 @@ static nsresult GenerateType3Msg(const nsString& domain,
   uint8_t ntlmv2Resp[NTLMv2_RESP_LEN];
   uint8_t ntlmHash[NTLM_HASH_LEN];
   uint8_t ntlmv2_blob1[NTLMv2_BLOB1_LEN];
+
+  memset(ntlmv2Resp, 0, NTLMv2_RESP_LEN);
   if (ntlmv2) {
     // NTLMv2 mode, the default
     nsString userUpper, domainUpper;