--- a/mfbt/Assertions.h
+++ b/mfbt/Assertions.h
@@ -441,24 +441,24 @@ struct AssertionConditionType
     (__VA_ARGS__))
 
 #ifdef DEBUG
 #  define MOZ_ASSERT(...) MOZ_RELEASE_ASSERT(__VA_ARGS__)
 #else
 #  define MOZ_ASSERT(...) do { } while (0)
 #endif /* DEBUG */
 
-#ifdef RELEASE_OR_BETA
+#if defined(NIGHTLY_BUILD) || defined(MOZ_DEV_EDITION)
+#  define MOZ_DIAGNOSTIC_ASSERT MOZ_RELEASE_ASSERT
+#  define MOZ_DIAGNOSTIC_ASSERT_ENABLED 1
+#else
 #  define MOZ_DIAGNOSTIC_ASSERT MOZ_ASSERT
 #  ifdef DEBUG
 #    define MOZ_DIAGNOSTIC_ASSERT_ENABLED 1
 #  endif
-#else
-#  define MOZ_DIAGNOSTIC_ASSERT MOZ_RELEASE_ASSERT
-#  define MOZ_DIAGNOSTIC_ASSERT_ENABLED 1
 #endif
 
 /*
  * MOZ_ASSERT_IF(cond1, cond2) is equivalent to MOZ_ASSERT(cond2) if cond1 is
  * true.
  *
  *   MOZ_ASSERT_IF(isPrime(num), num == 2 || isOdd(num));
  *