--- a/memory/build/mozjemalloc.cpp
+++ b/memory/build/mozjemalloc.cpp
@@ -2298,17 +2298,18 @@ arena_run_reg_dalloc(arena_run_t* run, a
   MOZ_DIAGNOSTIC_ASSERT(diff == regind * size);
   MOZ_DIAGNOSTIC_ASSERT(regind < bin->mRunNumRegions);
 
   elm = regind >> (LOG2(sizeof(int)) + 3);
   if (elm < run->mRegionsMinElement) {
     run->mRegionsMinElement = elm;
   }
   bit = regind - (elm << (LOG2(sizeof(int)) + 3));
-  MOZ_DIAGNOSTIC_ASSERT((run->mRegionsMask[elm] & (1U << bit)) == 0);
+  MOZ_RELEASE_ASSERT((run->mRegionsMask[elm] & (1U << bit)) == 0,
+                     "Double-free?");
   run->mRegionsMask[elm] |= (1U << bit);
 #undef SIZE_INV
 #undef SIZE_INV_SHIFT
 }
 
 bool
 arena_t::SplitRun(arena_run_t* aRun, size_t aSize, bool aLarge, bool aZero)
 {
@@ -3492,17 +3493,17 @@ arena_dalloc(void* aPtr, size_t aOffset,
   auto arena = chunk->arena;
   MOZ_ASSERT(arena);
   MOZ_DIAGNOSTIC_ASSERT(arena->mMagic == ARENA_MAGIC);
   MOZ_RELEASE_ASSERT(!aArena || arena == aArena);
 
   MutexAutoLock lock(arena->mLock);
   size_t pageind = aOffset >> gPageSize2Pow;
   arena_chunk_map_t* mapelm = &chunk->map[pageind];
-  MOZ_DIAGNOSTIC_ASSERT((mapelm->bits & CHUNK_MAP_ALLOCATED) != 0);
+  MOZ_RELEASE_ASSERT((mapelm->bits & CHUNK_MAP_ALLOCATED) != 0, "Double-free?");
   if ((mapelm->bits & CHUNK_MAP_LARGE) == 0) {
     // Small allocation.
     arena->DallocSmall(chunk, aPtr, mapelm);
   } else {
     // Large allocation.
     arena->DallocLarge(chunk, aPtr);
   }
 }
@@ -3891,17 +3892,17 @@ huge_dalloc(void* aPtr, arena_t* aArena)
   extent_node_t* node;
   {
     extent_node_t key;
     MutexAutoLock lock(huge_mtx);
 
     // Extract from tree of huge allocations.
     key.mAddr = aPtr;
     node = huge.Search(&key);
-    MOZ_ASSERT(node);
+    MOZ_RELEASE_ASSERT(node, "Double-free?");
     MOZ_ASSERT(node->mAddr == aPtr);
     MOZ_RELEASE_ASSERT(!aArena || node->mArena == aArena);
     huge.Remove(node);
 
     huge_allocated -= node->mSize;
     huge_mapped -= CHUNK_CEILING(node->mSize);
   }