diff --git a/docs/references/http-gateway-protocol-spec.md b/docs/references/http-gateway-protocol-spec.md
index 5e2043d..63d79ed 100644
--- a/docs/references/http-gateway-protocol-spec.md
+++ b/docs/references/http-gateway-protocol-spec.md
@@ -423,7 +423,7 @@ type StreamingCallbackHttpResponse = record {
 
 type StreamingStrategy = variant {
     Callback: record {
-        callback: func (StreamingToken) -> (opt StreamingCallbackHttpResponse) query;
+        callback: func (StreamingToken) -> (StreamingCallbackHttpResponse) query;
         token: StreamingToken;
     };
 };
@@ -509,7 +509,7 @@ type StreamingCallbackHttpResponse = record {
 
 type StreamingStrategy = variant {
     Callback: record {
-        callback: func (StreamingToken) -> (opt StreamingCallbackHttpResponse) query;
+        callback: func (StreamingToken) -> (StreamingCallbackHttpResponse) query;
         token: StreamingToken;
     };
 };
diff --git a/public/references/http-gateway.did b/public/references/http-gateway.did
index 3ec2d9c..9e2e305 100644
--- a/public/references/http-gateway.did
+++ b/public/references/http-gateway.did
@@ -38,7 +38,7 @@ type StreamingCallbackHttpResponse = record {
 
 type StreamingStrategy = variant {
   Callback: record {
-    callback: func (StreamingToken) -> (opt StreamingCallbackHttpResponse) query;
+    callback: func (StreamingToken) -> (StreamingCallbackHttpResponse) query;
     token: StreamingToken;
   };
 };