diff --git a/js/src/vm/StructuredClone.cpp b/js/src/vm/StructuredClone.cpp
index 7d9ba4da3657..7c767f7bc963 100644
--- a/js/src/vm/StructuredClone.cpp
+++ b/js/src/vm/StructuredClone.cpp
@@ -31,6 +31,7 @@
 
 #include "mozilla/Endian.h"
 #include "mozilla/FloatingPoint.h"
+#include "mozilla/TypedEnum.h"
 
 #include <algorithm>
 
@@ -53,7 +54,7 @@ using mozilla::LittleEndian;
 using mozilla::NativeEndian;
 using JS::CanonicalizeNaN;
 
-enum StructuredDataType {
+enum StructuredDataType MOZ_ENUM_TYPE(uint32_t) {
     /* Structured data types provided by the engine */
     SCTAG_FLOAT_MAX = 0xFFF00000,
     SCTAG_NULL = 0xFFFF0000,