diff --git a/js/public/Value.h b/js/public/Value.h
index 7d0b2abd6d65..70fe02d10ac7 100644
--- a/js/public/Value.h
+++ b/js/public/Value.h
@@ -237,7 +237,7 @@ typedef enum JSWhyMagic
     JS_WHY_MAGIC_COUNT
 } JSWhyMagic;
 
-#if defined(IS_LITTLE_ENDIAN)
+#if defined(MOZ_LITTLE_ENDIAN)
 # if defined(JS_NUNBOX32)
 typedef union jsval_layout
 {
@@ -285,7 +285,7 @@ typedef union jsval_layout
     uintptr_t asUIntPtr;
 } JSVAL_ALIGNMENT jsval_layout;
 # endif  /* JS_PUNBOX64 */
-#else   /* defined(IS_LITTLE_ENDIAN) */
+#else   /* defined(MOZ_LITTLE_ENDIAN) */
 # if defined(JS_NUNBOX32)
 typedef union jsval_layout
 {
@@ -331,7 +331,7 @@ typedef union jsval_layout
     uintptr_t asUIntPtr;
 } JSVAL_ALIGNMENT jsval_layout;
 # endif /* JS_PUNBOX64 */
-#endif  /* defined(IS_LITTLE_ENDIAN) */
+#endif  /* defined(MOZ_LITTLE_ENDIAN) */
 
 JS_STATIC_ASSERT(sizeof(jsval_layout) == 8);
 
diff --git a/js/src/jit/Lowering.cpp b/js/src/jit/Lowering.cpp
index 2f48af4fa294..ec2f5b43ec17 100644
--- a/js/src/jit/Lowering.cpp
+++ b/js/src/jit/Lowering.cpp
@@ -66,7 +66,7 @@ LIRGenerator::visitParameter(MParameter* param)
 
     offset *= sizeof(Value);
 #if defined(JS_NUNBOX32)
-# if defined(IS_BIG_ENDIAN)
+# if defined(MOZ_BIG_ENDIAN)
     ins->getDef(0)->setOutput(LArgument(offset));
     ins->getDef(1)->setOutput(LArgument(offset + 4));
 # else
diff --git a/js/src/jit/MacroAssembler.h b/js/src/jit/MacroAssembler.h
index 0761332d629e..cfb9788d88ac 100644
--- a/js/src/jit/MacroAssembler.h
+++ b/js/src/jit/MacroAssembler.h
@@ -179,7 +179,7 @@ using mozilla::FloatingPoint;
 # define PER_SHARED_ARCH DEFINED_ON(ALL_SHARED_ARCH)
 
 
-#ifdef IS_LITTLE_ENDIAN
+#ifdef MOZ_LITTLE_ENDIAN
 #define IMM32_16ADJ(X) X << 16
 #else
 #define IMM32_16ADJ(X) X
diff --git a/js/src/jsatom.cpp b/js/src/jsatom.cpp
index 9ef03ddf904b..895b7d03ecbe 100644
--- a/js/src/jsatom.cpp
+++ b/js/src/jsatom.cpp
@@ -568,7 +568,7 @@ js::XDRAtom(XDRState<mode>* xdr, MutableHandleAtom atomp)
         const Latin1Char* chars = reinterpret_cast<const Latin1Char*>(xdr->buf.read(length));
         atom = AtomizeChars(cx, chars, length);
     } else {
-#if IS_LITTLE_ENDIAN
+#if MOZ_LITTLE_ENDIAN
         /* Directly access the little endian chars in the XDR buffer. */
         const char16_t* chars = reinterpret_cast<const char16_t*>(xdr->buf.read(length * sizeof(char16_t)));
         atom = AtomizeChars(cx, chars, length);
@@ -596,7 +596,7 @@ js::XDRAtom(XDRState<mode>* xdr, MutableHandleAtom atomp)
         atom = AtomizeChars(cx, chars, length);
         if (chars != stackChars)
             js_free(chars);
-#endif /* !IS_LITTLE_ENDIAN */
+#endif /* !MOZ_LITTLE_ENDIAN */
     }
 
     if (!atom)
diff --git a/js/src/jscpucfg.h b/js/src/jscpucfg.h
index 660187ca60cf..80fdf6bb88b5 100644
--- a/js/src/jscpucfg.h
+++ b/js/src/jscpucfg.h
@@ -9,16 +9,6 @@
 
 #include "mozilla/EndianUtils.h"
 
-#if defined(MOZ_LITTLE_ENDIAN)
-# define IS_LITTLE_ENDIAN 1
-# undef  IS_BIG_ENDIAN
-#elif defined(MOZ_BIG_ENDIAN)
-# undef  IS_LITTLE_ENDIAN
-# define IS_BIG_ENDIAN 1
-#else
-# error "Cannot determine endianness of your platform. Please add support to jscpucfg.h."
-#endif
-
 #ifndef JS_STACK_GROWTH_DIRECTION
 # ifdef __hppa
 #  define JS_STACK_GROWTH_DIRECTION (1)
diff --git a/js/src/jsdtoa.cpp b/js/src/jsdtoa.cpp
index 6d0d950b474e..4d0a00621726 100644
--- a/js/src/jsdtoa.cpp
+++ b/js/src/jsdtoa.cpp
@@ -16,7 +16,7 @@
 
 using namespace js;
 
-#ifdef IS_LITTLE_ENDIAN
+#ifdef MOZ_LITTLE_ENDIAN
 #define IEEE_8087
 #else
 #define IEEE_MC68k
diff --git a/js/src/vm/TypedArrayObject.cpp b/js/src/vm/TypedArrayObject.cpp
index 954b4081b15b..4f5dbf84d3ad 100644
--- a/js/src/vm/TypedArrayObject.cpp
+++ b/js/src/vm/TypedArrayObject.cpp
@@ -1784,7 +1784,7 @@ DataViewObject::getDataPointer(JSContext* cx, Handle<DataViewObject*> obj, doubl
 static inline bool
 needToSwapBytes(bool littleEndian)
 {
-#if IS_LITTLE_ENDIAN
+#if MOZ_LITTLE_ENDIAN
     return !littleEndian;
 #else
     return littleEndian;