diff --git a/docker/Dockerfile b/docker/Dockerfile
index 1114987..0737cb4 100644
--- a/docker/Dockerfile
+++ b/docker/Dockerfile
@@ -6,7 +6,7 @@ RUN chown -R node /usr/src/app
 
 RUN apk add --no-cache tini
 
-RUN npm install -g npm && npm install -g wire.io@latest
+RUN npm install -g npm && npm install -g wire.io@3.3.1
 
 USER node
 
diff --git a/src/__snapshots__/client.test.js.snap b/src/__snapshots__/client.test.js.snap
index 77eaaef..a282deb 100644
--- a/src/__snapshots__/client.test.js.snap
+++ b/src/__snapshots__/client.test.js.snap
@@ -1,11 +1,13 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
-exports[`Client should call remote first function 1`] = `undefined`;
+exports[`Client should call remote first function 1`] = `"Function testrpc is not registered"`;
 
-exports[`Client should call remote last function 1`] = `undefined`;
+exports[`Client should call remote last function 1`] = `"Function testrpc is not registered"`;
 
-exports[`Client should call remote random function 1`] = `undefined`;
+exports[`Client should call remote random function 1`] = `"Function testrpc is not registered"`;
 
-exports[`Client should not be able to register different function type 1`] = `undefined`;
+exports[`Client should not be able to register different function type 1`] = `"Can't register a new function under the testrpc with this invoke value."`;
 
-exports[`Client should not be able to register different function type 2`] = `undefined`;
+exports[`Client should not be able to register different function type 2`] = `"Function testrpc already exists"`;
+
+exports[`Client should not be able to register different function type 3`] = `"Function testrpc is not registered"`;
diff --git a/src/client.js b/src/client.js
index 051890a..a5ea6d8 100644
--- a/src/client.js
+++ b/src/client.js
@@ -105,6 +105,7 @@ class Wire {
    */
   async register(name, callback, { invoke = 'single' } = {}) {
     // Add to locally registered callback
+
     this.registeredRPC[name] = callback;
 
     await this._callServerRPC('register', {
@@ -114,8 +115,10 @@ class Wire {
 
     // Return unregister callback
     const unregisterCallback = () => {
-      delete this.registeredRPC[name];
-      return this._callServerRPC('unregister', { name });
+      if (this.registeredRPC[name] === callback) {
+        delete this.registeredRPC[name];
+        return this._callServerRPC('unregister', { name });
+      }
     };
 
     this.toUnregister.push(unregisterCallback);
diff --git a/src/client.test.js b/src/client.test.js
index 9ba2141..988cc62 100644
--- a/src/client.test.js
+++ b/src/client.test.js
@@ -243,7 +243,7 @@ describe('Client', () => {
       retry(() => room3.call('testrpc'))
         .withTimeout(1000)
         .until((result) => expect(result).toEqual({}))
-    ).rejects.toThrowErrorMatchingSnapshot();
+    ).rejects.toMatchSnapshot();
   });
 
   it('should call remote last function', async () => {
@@ -292,7 +292,7 @@ describe('Client', () => {
       retry(() => room3.call('testrpc'))
         .withTimeout(1000)
         .until((result) => expect(result).toEqual({}))
-    ).rejects.toThrowErrorMatchingSnapshot();
+    ).rejects.toMatchSnapshot();
   });
 
   it('should call remote random function', async () => {
@@ -341,7 +341,7 @@ describe('Client', () => {
       retry(() => room3.call('testrpc'))
         .withTimeout(1000)
         .until((result) => expect(result).toEqual({}))
-    ).rejects.toThrowErrorMatchingSnapshot();
+    ).rejects.toMatchSnapshot();
   });
 
   it('should not be able to register different function type', async () => {
@@ -365,7 +365,7 @@ describe('Client', () => {
         },
         { invoke: 'first' }
       )
-    ).rejects.toThrowErrorMatchingSnapshot();
+    ).rejects.toMatchSnapshot();
 
     await unregister1();
 
@@ -377,10 +377,33 @@ describe('Client', () => {
     expect(result).toEqual({ answer: 46 });
 
     await expect(
-      room1.register('testrpc', (params) => {
+      room2.register('testrpc', (params) => {
         return { answer: 47 };
       })
-    ).rejects.toThrowErrorMatchingSnapshot();
+    ).rejects.toMatchSnapshot();
+
+    // We should be able to replace a single RPC from the registerer
+    const unregister2 = await room1.register('testrpc', (params) => {
+      return { answer: 47 };
+    });
+
+    result = await room3.call('testrpc');
+    expect(result).toEqual({ answer: 47 });
+
+    const unregister3 = await room1.register('testrpc', (params) => {
+      return { answer: 48 };
+    });
+
+    // If we unregister after the function has been replaced it shouldn't unregister
+    // the existing function
+    await unregister2();
+
+    result = await room3.call('testrpc');
+    expect(result).toEqual({ answer: 48 });
+
+    await unregister3();
+
+    await expect(room3.call('testrpc')).rejects.toMatchSnapshot();
   });
 
   it('should call onMaster callback on leave and disconnect', async () => {
diff --git a/src/server.js b/src/server.js
index 8727e1f..6253635 100644
--- a/src/server.js
+++ b/src/server.js
@@ -56,6 +56,7 @@ export const handleWire = (
      */
     const register = ({ name, invoke = 'single' }) => {
       const existingInvoke = rooms[roomName].rpc[name]?.invoke;
+      const existingCallbacks = rooms[roomName].rpc[name]?.callbacks || [];
 
       if (existingInvoke && invoke !== existingInvoke) {
         throw new Error(
@@ -63,8 +64,9 @@ export const handleWire = (
         );
       }
       if (
-        existingInvoke == 'single' &&
-        rooms[roomName].rpc[name].callbacks.length >= 1
+        existingInvoke === 'single' &&
+        existingCallbacks.length >= 1 &&
+        existingCallbacks[0] !== registeredRPCs[name]
       ) {
         throw new Error(`Function ${name} already exists`);
       }