diff --git a/server/ServerSession.ts b/server/ServerSession.ts
index 92ad563..4bec7a3 100644
--- a/server/ServerSession.ts
+++ b/server/ServerSession.ts
@@ -2919,7 +2919,7 @@ export function remote(targetOrOptions?: RemoteMethodOptions | ServerSession, me
  */
 export function free(resource: (...args: any[]) => any | Readable_fromNodePackage | Readable_fromReadableStreamPackage | ReadableStream | ReadableStreamDefaultReader) { // TODO: list writables
     if(typeof resource === "function") {
-        const clientCallback = resource as ClientCallback;
+        const clientCallback = (resource as Partial<WithTrimmedClientCallback>)[withTrimSourceCallback] ?? (resource as ClientCallback);
         if(clientCallback.socketConnection === undefined) { //
             throw new Error("The passed argument is not a client callback function.")
         }
@@ -2932,6 +2932,21 @@ export function free(resource: (...args: any[]) => any | Readable_fromNodePackag
 
 export type UnknownFunction = (...args: unknown[]) => unknown
 
+const withTrimSourceCallback = Symbol("withTrimSourceCallback");
+
+type WithTrimmedClientCallback = ClientCallback & {
+    [withTrimSourceCallback]: ClientCallback;
+};
+
+type WithTrimCacheEntry = {
+    trimArguments: boolean;
+    trimResult: boolean;
+    useSignatureFrom?: UnknownFunction;
+    wrapped: WithTrimmedClientCallback;
+}
+
+const withTrimCache = new WeakMap<ClientCallback, WithTrimCacheEntry[]>();
+
 /**
  * Returns a version where, during call, extra properties get trimmed off the arguments or result, so they don't produce a validation error.
  * <p>
@@ -2949,9 +2964,8 @@ export type UnknownFunction = (...args: unknown[]) => unknown
  * </code></pre>
  *
  * <p>
- *     Note: withTrim creates a new function instance every time. So i.e. you can't hand these to addEventListener(...) + removeEventListener(...) registries then.
- *     TODO: This could be improved for convenience. But is it really worth it ? Star this issue then: https://github.com/bogeeee/restfuncs/issues/8
- *     TODO: In that case, also make the util/EventEmitter class's resource-freeing mechanism aware of these derivatives.
+ *     Note: withTrim returns the same wrapped function instance when called repeatedly with the same callback and options.
+ *     This allows it to be used with addEventListener(...) + removeEventListener(...) style registries.
  * </p>
  * @param callbackFn
  * @param trimArguments
@@ -2977,11 +2991,36 @@ export function withTrim<CB extends UnknownFunction>(callbackFn: CB, trimArgumen
     }
 
     const clientCallback = callbackFn as any as ClientCallback;
+    let entries = withTrimCache.get(clientCallback);
+    if(entries === undefined) {
+        entries = [];
+        withTrimCache.set(clientCallback, entries);
+    }
+
+    const existing = entries.find(entry =>
+        entry.trimArguments === trimArguments &&
+        entry.trimResult === trimResult &&
+        entry.useSignatureFrom === useSignatureFrom
+    );
+    if(existing !== undefined) {
+        return existing.wrapped as any as CB;
+    }
 
     //@ts-ignore
-    return (...args: unknown[]) => {
+    const wrapped: WithTrimmedClientCallback = ((...args: unknown[]) => {
         return clientCallback._validateAndCall(args, trimArguments, trimResult, useSignatureFrom);
-    }
+    }) as WithTrimmedClientCallback;
+    wrapped[withTrimSourceCallback] = clientCallback;
+    wrapped._type = clientCallback._type;
+    wrapped.id = clientCallback.id;
+    wrapped.socketConnection = clientCallback.socketConnection;
+    wrapped.free = () => free(clientCallback);
+    wrapped._handedUpViaRemoteMethods = clientCallback._handedUpViaRemoteMethods;
+    wrapped._validateAndCall = (args, _trimArguments, _trimResult, _useSignatureForTrim, diagnosis) =>
+        clientCallback._validateAndCall(args, trimArguments, trimResult, useSignatureFrom, diagnosis);
+
+    entries.push({trimArguments, trimResult, useSignatureFrom, wrapped});
+    return wrapped as any as CB;
 }
 
 /**
@@ -3074,4 +3113,4 @@ function checkIfSecurityFieldsAreValid(session: SecurityRelevantSessionFields) {
 
 export function isClientCallback(fn: UnknownFunction) {
     return ((fn as ClientCallback).socketConnection !== undefined);
-}
\ No newline at end of file
+}
diff --git a/tests/clientServer/runtime-typechecking.test.ts b/tests/clientServer/runtime-typechecking.test.ts
index 7689b86..7e43914 100644
--- a/tests/clientServer/runtime-typechecking.test.ts
+++ b/tests/clientServer/runtime-typechecking.test.ts
@@ -1,6 +1,6 @@
 import { tags } from "typia";
 import 'reflect-metadata'
-import {ClientCallback, ServerSession} from "restfuncs-server";
+import {ClientCallback, ClientCallbackSet, ServerSession} from "restfuncs-server";
 import {withTrim} from "restfuncs-server/ServerSession";
 import express from "express";
 import {reflect} from "typescript-rtti";
@@ -781,6 +781,21 @@ describe("callbacks", () => {
             withTrim(cb)(objWithExtraProps);
             return objWithExtraProps.extraProp === "extra"; // is still intact ?
         }
+
+        @remote()
+        withTrimCanBeRemovedFromCallbackSet(cb: (obj: {x: string}) => void) {
+            const callbackSet = new ClientCallbackSet<[obj: {x: string}]>();
+            const added = withTrim(cb);
+            const removed = withTrim(cb);
+
+            callbackSet.add(added);
+
+            return {
+                sameWrapper: added === removed,
+                removed: callbackSet.remove(removed),
+                size: callbackSet.size,
+            };
+        }
     }
 
     it("should allow legal args in a simple callback", () => runClientServerTests(new ServerAPI, async (apiProxy) => {
@@ -929,6 +944,16 @@ describe("callbacks", () => {
     }, {
         useSocket: true
     }));
+
+    test("withTrim should return stable wrappers for callback registries", () => runClientServerTests(new ServerAPI, async (apiProxy) => {
+        await expect(apiProxy.withTrimCanBeRemovedFromCallbackSet((dummy: any) => {})).resolves.toStrictEqual({
+            sameWrapper: true,
+            removed: true,
+            size: 0,
+        });
+    }, {
+        useSocket: true
+    }));
 });
 
 describe("callbacks with mixed security requirements", () => {
@@ -1138,4 +1163,4 @@ test('Test anonymous object as service', async () => {
         }
     );
 })
-*/
\ No newline at end of file
+*/