--- a/js/src/jit/IonCode.h
+++ b/js/src/jit/IonCode.h
@@ -17,16 +17,20 @@
 #include "jit/ExecutableAllocator.h"
 #include "jit/ICStubSpace.h"
 #include "jit/IonOptimizationLevels.h"
 #include "jit/IonTypes.h"
 #include "js/UbiNode.h"
 #include "vm/TraceLogging.h"
 #include "vm/TypeInference.h"
 
+#ifndef __GNUC__
+#define __attribute__(x)
+#endif
+
 namespace js {
 namespace jit {
 
 class MacroAssembler;
 class PatchableBackedge;
 class IonBuilder;
 class IonICEntry;
 
@@ -156,17 +160,18 @@ class JitCode : public gc::TenuredCell
     // object can be allocated, nullptr is returned. On failure, |pool| is
     // automatically released, so the code may be freed.
     template <AllowGC allowGC>
     static JitCode* New(JSContext* cx, uint8_t* code, uint32_t bufferSize, uint32_t headerSize,
                         ExecutablePool* pool, CodeKind kind);
 
   public:
     static const JS::TraceKind TraceKind = JS::TraceKind::JitCode;
-};
+
+} __attribute__ ((aligned(4))); /* ensure alignment is at least 4 bytes */
 
 class SnapshotWriter;
 class RecoverWriter;
 class SafepointWriter;
 class SafepointIndex;
 class OsiIndex;
 class IonCache;
 class IonIC;