diff --git a/packages/react-dom/src/events/__tests__/DOMPluginEventSystem-test.internal.js b/packages/react-dom/src/events/__tests__/DOMPluginEventSystem-test.internal.js
index 8bf16bc94255c..004f0bb631f31 100644
--- a/packages/react-dom/src/events/__tests__/DOMPluginEventSystem-test.internal.js
+++ b/packages/react-dom/src/events/__tests__/DOMPluginEventSystem-test.internal.js
@@ -1669,16 +1669,28 @@ describe('DOMPluginEventSystem', () => {
 
             function Test() {
               React.useEffect(() => {
-                setClick1(buttonRef.current, targetListener1);
-                setClick2(buttonRef.current, targetListener2);
-                setClick3(buttonRef.current, targetListener3);
-                setClick4(buttonRef.current, targetListener4);
+                const clearClick1 = setClick1(
+                  buttonRef.current,
+                  targetListener1,
+                );
+                const clearClick2 = setClick2(
+                  buttonRef.current,
+                  targetListener2,
+                );
+                const clearClick3 = setClick3(
+                  buttonRef.current,
+                  targetListener3,
+                );
+                const clearClick4 = setClick4(
+                  buttonRef.current,
+                  targetListener4,
+                );
 
                 return () => {
-                  setClick1();
-                  setClick2();
-                  setClick3();
-                  setClick4();
+                  clearClick1();
+                  clearClick2();
+                  clearClick3();
+                  clearClick4();
                 };
               });
 
@@ -1703,16 +1715,28 @@ describe('DOMPluginEventSystem', () => {
 
             function Test2() {
               React.useEffect(() => {
-                setClick1(buttonRef.current, targetListener1);
-                setClick2(buttonRef.current, targetListener2);
-                setClick3(buttonRef.current, targetListener3);
-                setClick4(buttonRef.current, targetListener4);
+                const clearClick1 = setClick1(
+                  buttonRef.current,
+                  targetListener1,
+                );
+                const clearClick2 = setClick2(
+                  buttonRef.current,
+                  targetListener2,
+                );
+                const clearClick3 = setClick3(
+                  buttonRef.current,
+                  targetListener3,
+                );
+                const clearClick4 = setClick4(
+                  buttonRef.current,
+                  targetListener4,
+                );
 
                 return () => {
-                  setClick1();
-                  setClick2();
-                  setClick3();
-                  setClick4();
+                  clearClick1();
+                  clearClick2();
+                  clearClick3();
+                  clearClick4();
                 };
               });
 
diff --git a/packages/react-reconciler/src/ReactFiberWorkLoop.new.js b/packages/react-reconciler/src/ReactFiberWorkLoop.new.js
index f7a4f39bb1cba..0f881d853426c 100644
--- a/packages/react-reconciler/src/ReactFiberWorkLoop.new.js
+++ b/packages/react-reconciler/src/ReactFiberWorkLoop.new.js
@@ -2844,6 +2844,22 @@ export function captureCommitPhaseError(sourceFiber: Fiber, error: mixed) {
     }
     fiber = fiber.return;
   }
+
+  if (__DEV__) {
+    // TODO: Until we re-land skipUnmountedBoundaries (see #20147), this warning
+    // will fire for errors that are thrown by destroy functions inside deleted
+    // trees. What it should instead do is propagate the error to the parent of
+    // the deleted tree. In the meantime, do not add this warning to the
+    // allowlist; this is only for our internal use.
+    console.error(
+      'Internal React error: Attempted to capture a commit phase error ' +
+        'inside a detached tree. This indicates a bug in React. Likely ' +
+        'causes include deleting the same fiber more than once, committing an ' +
+        'already-finished tree, or an inconsistent return pointer.\n\n' +
+        'Error message:\n\n%s',
+      error,
+    );
+  }
 }
 
 export function pingSuspendedRoot(