diff --git a/js/src/gc/Barrier-inl.h b/js/src/gc/Barrier-inl.h
index 66e07a8472d..bdc48633d3d 100644
--- a/js/src/gc/Barrier-inl.h
+++ b/js/src/gc/Barrier-inl.h
@@ -16,6 +16,13 @@
 
 namespace js {
 
+template <typename T, typename Unioned>
+void
+EncapsulatedPtr<T, Unioned>::pre()
+{
+    T::writeBarrierPre(value);
+}
+
 template <typename T>
 inline void
 RelocatablePtr<T>::post()
diff --git a/js/src/gc/Barrier.h b/js/src/gc/Barrier.h
index 4f238f47d2b..443cddb7a3f 100644
--- a/js/src/gc/Barrier.h
+++ b/js/src/gc/Barrier.h
@@ -173,7 +173,7 @@ class EncapsulatedPtr
     operator T*() const { return value; }
 
   protected:
-    void pre() { T::writeBarrierPre(value); }
+    void pre();
 };
 
 template <class T, class Unioned = uintptr_t>