--- a/netwerk/cookie/nsCookieService.cpp
+++ b/netwerk/cookie/nsCookieService.cpp
@@ -2,16 +2,17 @@
 /* vim: set sw=2 ts=8 et tw=80 : */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "mozilla/Attributes.h"
 #include "mozilla/DebugOnly.h"
 #include "mozilla/Likely.h"
+#include "mozilla/Printf.h"
 #include "mozilla/Unused.h"
 
 #include "mozilla/net/CookieServiceChild.h"
 #include "mozilla/net/NeckoCommon.h"
 
 #include "nsCookieService.h"
 #include "nsContentUtils.h"
 #include "nsIServiceManager.h"
@@ -322,20 +323,20 @@ LogSuccess(bool aSetCookie, nsIURI *aHos
   LogSuccess(aSetCookie, aHostURI, aCookieString.get(), aCookie, aReplacing);
 }
 
 #ifdef DEBUG
 #define NS_ASSERT_SUCCESS(res)                                               \
   PR_BEGIN_MACRO                                                             \
   nsresult __rv = res; /* Do not evaluate |res| more than once! */           \
   if (NS_FAILED(__rv)) {                                                     \
-    char *msg = PR_smprintf("NS_ASSERT_SUCCESS(%s) failed with result 0x%X", \
-                            #res, __rv);                                     \
+    char *msg = mozilla::Smprintf("NS_ASSERT_SUCCESS(%s) failed with result 0x%" PRIX32, \
+                           #res, static_cast<uint32_t>(__rv));               \
     NS_ASSERTION(NS_SUCCEEDED(__rv), msg);                                   \
-    PR_smprintf_free(msg);                                                   \
+    mozilla::SmprintfFree(msg);                                                    \
   }                                                                          \
   PR_END_MACRO
 #else
 #define NS_ASSERT_SUCCESS(res) PR_BEGIN_MACRO /* nothing */ PR_END_MACRO
 #endif
 
 /******************************************************************************
  * DBListenerErrorHandler impl: