diff --git a/libs/core/output.ts b/libs/core/output.ts
index c5f82039..5213658c 100644
--- a/libs/core/output.ts
+++ b/libs/core/output.ts
@@ -99,4 +99,10 @@ namespace output {
         }
         writePWM(b)
     }
+}
+
+
+interface Buffer {
+    [index: number]: number;
+    // rest defined in buffer.cpp
 }
\ No newline at end of file