--- a/toolkit/mozapps/update/common/pathhash.cpp
+++ b/toolkit/mozapps/update/common/pathhash.cpp
@@ -39,17 +39,17 @@ static BOOL
 CalculateMD5(const char *data, DWORD dataSize,
              BYTE **hash, DWORD &hashSize)
 {
   HCRYPTPROV hProv = 0;
   HCRYPTHASH hHash = 0;
 
   if (!CryptAcquireContext(&hProv, nullptr, nullptr, PROV_RSA_FULL,
                            CRYPT_VERIFYCONTEXT)) {
-    if (NTE_BAD_KEYSET != GetLastError()) {
+    if ((DWORD)NTE_BAD_KEYSET != GetLastError()) {
       return FALSE;
     }
 
     // Maybe it doesn't exist, try to create it.
     if (!CryptAcquireContext(&hProv, nullptr, nullptr, PROV_RSA_FULL,
                              CRYPT_VERIFYCONTEXT | CRYPT_NEWKEYSET)) {
       return FALSE;
     }