diff --git a/wasm/tester.js b/wasm/tester.js
index f01ba2e..71e14b2 100644
--- a/wasm/tester.js
+++ b/wasm/tester.js
@@ -87,6 +87,9 @@ async function compile (fileName, options) {
 	      if (options.verbose) {
             console.log(b.stdout);
 	      }
+	      if (b.stderr != '') {
+		        throw(b.stderr);
+        }
     } catch (e) {
 	      assert(false,
 	             "circom compiler error \n" + e);