diff --git a/Source/WTF/wtf/RunLoop.h b/Source/WTF/wtf/RunLoop.h
index 0c67601ff6d02..110163098d3b5 100644
--- a/Source/WTF/wtf/RunLoop.h
+++ b/Source/WTF/wtf/RunLoop.h
@@ -195,6 +195,11 @@ class WTF_CAPABILITY("is current") RunLoop final : public GuaranteedSerialFuncti
 #elif USE(BUN_EVENT_LOOP)
         // WTFTimer in Timer.zig
         struct Bun__WTFTimer;
+        // Called from stop() once the backend has removed a still-armed timer
+        // from its heap, i.e. fired() is not running and will not run. Used by
+        // DispatchTimer to drop the self-ref dispatchAfter() stores in
+        // m_function; other subclasses have nothing to release.
+        virtual void didStopWhileActive() { }
 #endif
 
         ASCIILiteral description() const { return m_description; }
@@ -337,6 +342,13 @@ class WTF_CAPABILITY("is current") RunLoop final : public GuaranteedSerialFuncti
         }
     private:
         void fired() final { m_function(); }
+#if USE(BUN_EVENT_LOOP)
+        // dispatchAfter() captures a Ref to this timer inside m_function;
+        // dropping it here breaks the cycle when a caller stops the timer
+        // before it fires. stop() only calls this once the Bun-side heap has
+        // removed the still-armed node, so m_function is not on any stack.
+        void didStopWhileActive() final { m_function = { }; }
+#endif
 
         Function<void()> m_function;
     };
diff --git a/Source/WTF/wtf/bun/RunLoopBun.cpp b/Source/WTF/wtf/bun/RunLoopBun.cpp
index 6127aff064c78..6315ccb312665 100644
--- a/Source/WTF/wtf/bun/RunLoopBun.cpp
+++ b/Source/WTF/wtf/bun/RunLoopBun.cpp
@@ -22,7 +22,9 @@ extern "C" __attribute__((weak)) void WTFTimer__update(RunLoop::TimerBase::Bun__
 extern "C" __attribute__((weak)) void WTFTimer__deinit(RunLoop::TimerBase::Bun__WTFTimer*);
 extern "C" __attribute__((weak)) bool WTFTimer__isActive(const RunLoop::TimerBase::Bun__WTFTimer*);
 extern "C" __attribute__((weak)) double WTFTimer__secondsUntilTimer(const RunLoop::TimerBase::Bun__WTFTimer*);
-extern "C" __attribute__((weak)) void WTFTimer__cancel(RunLoop::TimerBase::Bun__WTFTimer*);
+// Returns whether the timer was still armed in Bun's wtf_timers heap (i.e.
+// fired() has not been and will not be dispatched for it).
+extern "C" __attribute__((weak)) bool WTFTimer__cancel(RunLoop::TimerBase::Bun__WTFTimer*);
 
 // Weak, so that Bun can override it
 extern "C" __attribute__((weak)) bool Bun__thisThreadHasVM();
@@ -89,7 +91,8 @@ void RunLoop::TimerBase::stop()
         return stopGeneric();
     case Kind::Bun:
         if (auto* ref = std::get_if<std::reference_wrapper<Bun__WTFTimer>>(&m_impl)) {
-            WTFTimer__cancel(&ref->get());
+            if (WTFTimer__cancel(&ref->get()))
+                didStopWhileActive();
         }
         return;
     }