diff --git a/cli/pbjs.d.ts b/cli/pbjs.d.ts
index 5fbe06a73..ead1f3c5d 100644
--- a/cli/pbjs.d.ts
+++ b/cli/pbjs.d.ts
@@ -1,4 +1,4 @@
-type pbjsCallback = (err: Error|null, output?: string) => {};
+type pbjsCallback = (err: Error|null, output?: string) => void;
 
 /**
  * Runs pbjs programmatically.
diff --git a/cli/pbts.d.ts b/cli/pbts.d.ts
index a2a5f7cb2..35db28c0e 100644
--- a/cli/pbts.d.ts
+++ b/cli/pbts.d.ts
@@ -1,4 +1,4 @@
-type pbtsCallback = (err: Error|null, output?: string) => {};
+type pbtsCallback = (err: Error|null, output?: string) => void;
 
 /**
  * Runs pbts programmatically.