--- a/js/src/gc/Nursery.cpp
+++ b/js/src/gc/Nursery.cpp
@@ -1374,17 +1374,17 @@ void js::Nursery::maybeResizeNursery(JS:
   // relationship that works for all programs and can be predicted in
   // advance doesn't exist.
   static const float GrowThreshold = 0.03f;
   static const float ShrinkThreshold = 0.01f;
   static const float PromotionGoal = (GrowThreshold + ShrinkThreshold) / 2.0f;
   const float factor = promotionRate / PromotionGoal;
   MOZ_ASSERT(factor >= 0.0f);
 
-  MOZ_ASSERT((float(capacity()) * factor) <= SIZE_MAX);
+  MOZ_ASSERT((float(capacity()) * factor) <= float(SIZE_MAX));
   size_t newCapacity = size_t(float(capacity()) * factor);
 
   const size_t minNurseryBytes = roundSize(tunables().gcMinNurseryBytes());
   MOZ_ASSERT(minNurseryBytes >= ArenaSize);
 
   // If one of these conditions is true then we always shrink or grow the
   // nursery. This way the thresholds still have an effect even if the goal
   // seeking says the current size is ideal.