--- a/modules/libpref/prefapi.cpp
+++ b/modules/libpref/prefapi.cpp
@@ -778,18 +778,23 @@ PrefHashEntry* pref_HashTableLookup(cons
     MOZ_ASSERT(NS_IsMainThread());
 #endif
     MOZ_ASSERT((!XRE_IsContentProcess() || gPhase != START),
                "pref access before commandline prefs set");
     /* If you're hitting this assertion, you've added a pref access to start up.
      * Consider moving it later or add it to the whitelist in ContentPrefs.cpp
      * and get review from a DOM peer
      */
-    MOZ_ASSERT((!XRE_IsContentProcess() || gPhase > END_INIT_PREFS || gWatchingPref || inInitArray(key)),
-               "accessing non-init pref before the rest of the prefs are sent");
+#ifdef DEBUG
+    if (XRE_IsContentProcess() && gPhase <= END_INIT_PREFS &&
+        !gWatchingPref && !inInitArray(key)) {
+      MOZ_CRASH_UNSAFE_PRINTF("accessing non-init pref %s before the rest of the prefs are sent",
+                              key);
+    }
+#endif
     return static_cast<PrefHashEntry*>(gHashTable->Search(key));
 }
 
 nsresult pref_HashPref(const char *key, PrefValue value, PrefType type, uint32_t flags)
 {
 #ifndef MOZ_B2G
     MOZ_ASSERT(NS_IsMainThread());
 #endif