diff --git a/js/src/jit/BitSet.h b/js/src/jit/BitSet.h
index c2f04650fd0f..b6bab6ec06bb 100644
--- a/js/src/jit/BitSet.h
+++ b/js/src/jit/BitSet.h
@@ -29,11 +29,11 @@ class BitSet : private TempObject
 
   private:
     BitSet(unsigned int numBits) :
-        numBits_(numBits),
-        bits_(nullptr) {}
+        bits_(nullptr),
+        numBits_(numBits) {}
 
-    unsigned int numBits_;
     uint32_t *bits_;
+    const unsigned int numBits_;
 
     static inline uint32_t bitForValue(unsigned int value) {
         return 1l << uint32_t(value % BitsPerWord);
diff --git a/js/src/jit/FixedList.h b/js/src/jit/FixedList.h
index b5da5e553785..4d336f7d0930 100644
--- a/js/src/jit/FixedList.h
+++ b/js/src/jit/FixedList.h
@@ -19,8 +19,8 @@ namespace jit {
 template <typename T>
 class FixedList
 {
-    size_t length_;
     T *list_;
+    size_t length_;
 
   private:
     FixedList(const FixedList&); // no copy definition.