diff --git a/gfx/2d/FilterNodeSoftware.cpp b/gfx/2d/FilterNodeSoftware.cpp
index fd5523fd9..0cb7ea904 100644
--- a/gfx/2d/FilterNodeSoftware.cpp
+++ b/gfx/2d/FilterNodeSoftware.cpp
@@ -2771,7 +2771,7 @@ FilterNodeArithmeticCombineSoftware::SetAttribute(uint32_t aIndex,
                                                   uint32_t aSize)
 {
   MOZ_ASSERT(aIndex == ATT_ARITHMETIC_COMBINE_COEFFICIENTS);
-  MOZ_ASSERT(aSize == 4);
+  MOZ_RELEASE_ASSERT(aSize == 4);
 
   mK1 = aFloat[0];
   mK2 = aFloat[1];
diff --git a/xpcom/glue/PLDHashTable.cpp b/xpcom/glue/PLDHashTable.cpp
index bf5d70c78..55b3308ea 100644
--- a/xpcom/glue/PLDHashTable.cpp
+++ b/xpcom/glue/PLDHashTable.cpp
@@ -220,17 +220,17 @@ PLDHashTable::operator=(PLDHashTable&& aOther)
     return *this;
   }
 
-  // Destruct |this|.
-  this->~PLDHashTable();
-
-  // |mOps| and |mEntrySize| are const so we can't assign them. Instead, we
-  // require that they are equal. The justification for this is that they're
+  // |mOps| and |mEntrySize| are required to stay the same, they're
   // conceptually part of the type -- indeed, if PLDHashTable was a templated
   // type like nsTHashtable, they *would* be part of the type -- so it only
   // makes sense to assign in cases where they match.
   MOZ_RELEASE_ASSERT(mOps == aOther.mOps);
   MOZ_RELEASE_ASSERT(mEntrySize == aOther.mEntrySize);
 
+  // Reconstruct |this|.
+  this->~PLDHashTable();
+  new (this) PLDHashTable(aOther.mOps, aOther.mEntrySize, 0);
+
   // Move non-const pieces over.
   mHashShift = Move(aOther.mHashShift);
   mEntryCount = Move(aOther.mEntryCount);