diff --git a/js/ipc/CPOWTimer.cpp b/js/ipc/CPOWTimer.cpp
index ad39c3d32e..e84f04e79f 100644
--- a/js/ipc/CPOWTimer.cpp
+++ b/js/ipc/CPOWTimer.cpp
@@ -10,16 +10,6 @@
 
 #include "jsapi.h"
 
-CPOWTimer::CPOWTimer(JSContext* cx MOZ_GUARD_OBJECT_NOTIFIER_PARAM_IN_IMPL)
-    : cx_(nullptr)
-    , startInterval_(0)
-{
-    MOZ_GUARD_OBJECT_NOTIFIER_INIT;
-    if (!js::GetStopwatchIsMonitoringCPOW(cx))
-        return;
-    cx_ = cx;
-    startInterval_ = JS_Now();
-}
 CPOWTimer::~CPOWTimer()
 {
     if (!cx_) {
diff --git a/js/ipc/CPOWTimer.h b/js/ipc/CPOWTimer.h
index 173f87b107..2755ee14ad 100644
--- a/js/ipc/CPOWTimer.h
+++ b/js/ipc/CPOWTimer.h
@@ -21,7 +21,16 @@
  */
 class MOZ_RAII CPOWTimer final {
   public:
-    explicit inline CPOWTimer(JSContext* cx MOZ_GUARD_OBJECT_NOTIFIER_PARAM);
+    explicit inline
+    CPOWTimer(JSContext* cx MOZ_GUARD_OBJECT_NOTIFIER_PARAM) : cx_(nullptr)
+                                                             , startInterval_(0)
+    {
+        MOZ_GUARD_OBJECT_NOTIFIER_INIT;
+        if (!js::GetStopwatchIsMonitoringCPOW(cx))
+            return;
+        cx_ = cx;
+        startInterval_ = JS_Now();
+    }
     ~CPOWTimer();
 
   private: