diff --git a/c/tester.js b/c/tester.js
index de68981..fe3cc01 100644
--- a/c/tester.js
+++ b/c/tester.js
@@ -202,7 +202,7 @@ function check_versions ( v1, v2 ) {
 }
 
 async function compiler_above_version(v) {
-    let output = await exec('circom --version').toString();
+    let output = (await exec('circom --version')).stdout;
     let compiler_version = version_to_list(output.slice(output.search(/\d/),-1));
     vlist = version_to_list(v);
     return check_versions ( compiler_version, vlist );
diff --git a/wasm/tester.js b/wasm/tester.js
index 8a41daf..52aaf9e 100644
--- a/wasm/tester.js
+++ b/wasm/tester.js
@@ -193,7 +193,7 @@ function check_versions ( v1, v2 ) {
 }
 
 async function compiler_above_version(v) {
-    let output = await exec('circom --version').toString();
+    let output = (await exec('circom --version')).stdout;
     let compiler_version = version_to_list(output.slice(output.search(/\d/),-1));
     vlist = version_to_list(v);
     return check_versions ( compiler_version, vlist );