diff --git a/js/public/GCAPI.h b/js/public/GCAPI.h
index 70c4fb525358..a156ea1d4d16 100644
--- a/js/public/GCAPI.h
+++ b/js/public/GCAPI.h
@@ -289,7 +289,7 @@ ExposeGCThingToActiveJS(void *thing, JSGCTraceKind kind)
      * All live objects in the nursery are moved to tenured at the beginning of
      * each GC slice, so the gray marker never sees nursery things.
      */
-    if (uintptr_t(thing) >= rt->gcNurseryStart_ && uintptr_t(thing) < rt->gcNurseryEnd_)
+    if (js::gc::IsInsideNursery(rt, thing))
         return;
 #endif
     if (IsIncrementalBarrierNeededOnGCThing(rt, thing, kind))
diff --git a/js/public/HeapAPI.h b/js/public/HeapAPI.h
index 057c7f3b6238..505c90af0e6f 100644
--- a/js/public/HeapAPI.h
+++ b/js/public/HeapAPI.h
@@ -149,6 +149,16 @@ GetGCThingArena(void *thing)
     return reinterpret_cast<JS::shadow::ArenaHeader *>(addr);
 }
 
+JS_ALWAYS_INLINE bool
+IsInsideNursery(const JS::shadow::Runtime *runtime, const void *p)
+{
+#ifdef JSGC_GENERATIONAL
+    return uintptr_t(p) >= runtime->gcNurseryStart_ && uintptr_t(p) < runtime->gcNurseryEnd_;
+#else
+    return false;
+#endif
+}
+
 } /* namespace gc */
 
 } /* namespace js */
@@ -178,7 +188,7 @@ GCThingIsMarkedGray(void *thing)
      * each GC slice, so the gray marker never sees nursery things.
      */
     JS::shadow::Runtime *rt = js::gc::GetGCThingRuntime(thing);
-    if (uintptr_t(thing) >= rt->gcNurseryStart_ && uintptr_t(thing) < rt->gcNurseryEnd_)
+    if (js::gc::IsInsideNursery(rt, thing))
         return false;
 #endif
     uintptr_t *word, mask;
diff --git a/js/src/gc/Heap.h b/js/src/gc/Heap.h
index e8be86561188..2ae6ac20b6fe 100644
--- a/js/src/gc/Heap.h
+++ b/js/src/gc/Heap.h
@@ -1049,7 +1049,7 @@ Cell::isTenured() const
 {
 #ifdef JSGC_GENERATIONAL
     JS::shadow::Runtime *rt = js::gc::GetGCThingRuntime(this);
-    return uintptr_t(this) < rt->gcNurseryStart_ || uintptr_t(this) >= rt->gcNurseryEnd_;
+    return !IsInsideNursery(rt, this);
 #endif
     return true;
 }
diff --git a/js/src/gc/Nursery.h b/js/src/gc/Nursery.h
index d2d802b261d5..d782691d5926 100644
--- a/js/src/gc/Nursery.h
+++ b/js/src/gc/Nursery.h
@@ -66,7 +66,7 @@ class Nursery
 
     template <typename T>
     JS_ALWAYS_INLINE bool isInside(const T *p) const {
-        return uintptr_t(p) >= start() && uintptr_t(p) < heapEnd();
+        return gc::IsInsideNursery((JS::shadow::Runtime *)runtime_, p);
     }
 
     /*
diff --git a/js/src/jsgcinlines.h b/js/src/jsgcinlines.h
index abab06b00ad0..b0cbd1c04667 100644
--- a/js/src/jsgcinlines.h
+++ b/js/src/jsgcinlines.h
@@ -91,15 +91,6 @@ ShouldNurseryAllocate(const Nursery &nursery, AllocKind kind, InitialHeap heap)
 }
 #endif
 
-inline bool
-IsInsideNursery(JSRuntime *rt, const void *thing)
-{
-#ifdef JSGC_GENERATIONAL
-    return rt->gcNursery.isInside(thing);
-#endif
-    return false;
-}
-
 inline JSGCTraceKind
 GetGCThingTraceKind(const void *thing)
 {