diff --git a/src/execution.ts b/src/execution.ts
index feb4bba..99acd35 100644
--- a/src/execution.ts
+++ b/src/execution.ts
@@ -260,12 +260,10 @@ async function executeFromQueue(channel: string) {
       // handle function calls
       if (generatedMessage.function_call) {
         OpenAImessages.push(generatedMessage);
-        OpenAImessages.push({
-          role: "function",
-          name: generatedMessage.function_call.name,
-          // FIXME: don't use new instance of FunctionManager
-          content: new FunctionManager().handleFunction(generatedMessage.function_call),
-        });
+        // FIXME: don't use new instance of FunctionManager
+        OpenAImessages.push(
+          new FunctionManager().handleFunction(generatedMessage.function_call)
+        );
       }
     } while (generatedMessage.function_call);
 
diff --git a/src/funcitonManager.ts b/src/funcitonManager.ts
index d351c15..4a0910e 100644
--- a/src/funcitonManager.ts
+++ b/src/funcitonManager.ts
@@ -1,4 +1,5 @@
-import { ChatCompletionFunctions, ChatCompletionRequestMessageFunctionCall } from "openai";
+import { ChatCompletionFunctions, ChatCompletionRequestMessage, ChatCompletionRequestMessageFunctionCall } from "openai";
+
 import config from "./config";
 
 type parameterMap = {
@@ -60,9 +61,20 @@ export default class FunctionManager {
     return rvalue;
   }
 
-  public handleFunction(request: ChatCompletionRequestMessageFunctionCall) {
+  public handleFunction(request: ChatCompletionRequestMessageFunctionCall): ChatCompletionRequestMessage {
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
     let parsedArguments: any;
+    
+    const functionToRun = this.store.get(request.name ?? "");
+
+    // check if the function is registered
+    if (!functionToRun) {
+      return {
+        role: "system",
+        content: "Only use functions that were provided to you",
+      };
+    }
+
     try {
       parsedArguments = JSON.parse(request.arguments ?? "");
     }
@@ -70,7 +82,11 @@ export default class FunctionManager {
       console.error("Function arguments raw: " + request.arguments);
       throw new Error(`Failed to parse the function JSON arguments when running function [${request.name}]`, {cause: e});
     }
-    return this.store.get(request.name ?? "")?.execute(parsedArguments);
+    return {
+      role: "function",
+      name: request.name,
+      content: functionToRun.execute(parsedArguments),
+    };
   }
 }