diff --git a/api/src/chat/schemas/types/pattern.ts b/api/src/chat/schemas/types/pattern.ts
index 7c43cf11..bb1f9e9a 100644
--- a/api/src/chat/schemas/types/pattern.ts
+++ b/api/src/chat/schemas/types/pattern.ts
@@ -32,9 +32,26 @@ export const nlpPatternSchema = z.discriminatedUnion('match', [
 
 export type NlpPattern = z.infer<typeof nlpPatternSchema>;
 
+export const stringRegexPatternSchema = z.string().refine(
+  (value) => {
+    if (value.startsWith('/') && value.endsWith('/')) {
+      if (value.length === 2) return false;
+      try {
+        new RegExp(value.slice(1, -1), 'gi');
+        return true;
+      } catch (err) {
+        return false;
+      }
+    }
+    return value !== '';
+  },
+  {
+    message: 'Invalid regex or empty string',
+  },
+);
+
 export const patternSchema = z.union([
-  z.string(),
-  z.instanceof(RegExp),
+  stringRegexPatternSchema,
   payloadPatternSchema,
   z.array(nlpPatternSchema),
 ]);
diff --git a/api/src/chat/services/block.service.ts b/api/src/chat/services/block.service.ts
index bab88387..2a604935 100644
--- a/api/src/chat/services/block.service.ts
+++ b/api/src/chat/services/block.service.ts
@@ -31,7 +31,7 @@ import {
   OutgoingMessageFormat,
   StdOutgoingEnvelope,
 } from '../schemas/types/message';
-import { NlpPattern, Pattern, PayloadPattern } from '../schemas/types/pattern';
+import { NlpPattern, PayloadPattern } from '../schemas/types/pattern';
 import { Payload, StdQuickReply } from '../schemas/types/quick-reply';
 import { SubscriberContext } from '../schemas/types/subscriberContext';
 
@@ -194,7 +194,7 @@ export class BlockService extends BaseService<
     block: Block | BlockFull,
   ): (RegExpMatchArray | string)[] | false {
     // Filter text patterns & Instanciate Regex patterns
-    const patterns: undefined | Pattern[] = block.patterns?.map((pattern) => {
+    const patterns = block.patterns?.map((pattern) => {
       if (
         typeof pattern === 'string' &&
         pattern.endsWith('/') &&