diff --git a/netwerk/base/src/nsSocketTransport2.cpp b/netwerk/base/src/nsSocketTransport2.cpp
index e40de07d1e1..9672d4cb705 100644
--- a/netwerk/base/src/nsSocketTransport2.cpp
+++ b/netwerk/base/src/nsSocketTransport2.cpp
@@ -130,7 +130,9 @@ IsNSSErrorCode(PRErrorCode code)
 static nsresult
 GetXPCOMFromNSSError(PRErrorCode code)
 {
-    return NS_ERROR_GENERATE_FAILURE(NS_ERROR_MODULE_SECURITY, -1 * code);
+    // XXX Don't make up nsresults, it's supposed to be an enum (bug 778113)
+    return (nsresult)NS_ERROR_GENERATE_FAILURE(NS_ERROR_MODULE_SECURITY,
+                                               -1 * code);
 }
 
 static nsresult
diff --git a/security/manager/ssl/src/NSSErrorsService.cpp b/security/manager/ssl/src/NSSErrorsService.cpp
index 7fa847b93e8..efd6c69e214 100644
--- a/security/manager/ssl/src/NSSErrorsService.cpp
+++ b/security/manager/ssl/src/NSSErrorsService.cpp
@@ -71,10 +71,11 @@ NSSErrorsService::GetXPCOMFromNSSError(PRInt32 aNSPRCode, nsresult *aXPCOMErrorC
 
   // The error codes within each module may be a 16 bit value.
   // For simplicity let's use the positive value of the NSS code.
+  // XXX Don't make up nsresults, it's supposed to be an enum (bug 778113)
 
   *aXPCOMErrorCode =
-    NS_ERROR_GENERATE_FAILURE(NS_ERROR_MODULE_SECURITY,
-                              -1 * aNSPRCode);
+    (nsresult)NS_ERROR_GENERATE_FAILURE(NS_ERROR_MODULE_SECURITY,
+                                        -1 * aNSPRCode);
   return NS_OK;
 }
 
diff --git a/toolkit/identity/IdentityCryptoService.cpp b/toolkit/identity/IdentityCryptoService.cpp
index fc4aa38b7c1..36a807f528a 100644
--- a/toolkit/identity/IdentityCryptoService.cpp
+++ b/toolkit/identity/IdentityCryptoService.cpp
@@ -70,7 +70,9 @@ PRErrorCode_to_nsresult(PRErrorCode error)
   }
 
   // From NSSErrorsService::GetXPCOMFromNSSError
-  return NS_ERROR_GENERATE_FAILURE(NS_ERROR_MODULE_SECURITY, -1 * error);
+  // XXX Don't make up nsresults, it's supposed to be an enum (bug 778113)
+  return (nsresult)NS_ERROR_GENERATE_FAILURE(NS_ERROR_MODULE_SECURITY,
+                                             -1 * error);
 }
 
 // IMPORTANT: This must be called immediately after the function returning the