diff --git a/EIPS/eip-1271.md b/EIPS/eip-1271.md
index 95546d33..2e9b159b 100644
--- a/EIPS/eip-1271.md
+++ b/EIPS/eip-1271.md
@@ -43,11 +43,12 @@ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "S
 *
 * MUST return a bool upon valid or invalid signature with corresponding _data
 * MUST take (bytes, bytes) as arguments
+* MUST allow external calls
 */ 
 function isValidSignature(
-	bytes _data, 
+    bytes _data, 
     bytes _signature)
-	public
+    public
     view 
     returns (bool isValid); 
 ```