diff --git a/src/which.js b/src/which.js
index 1591ebeb..cc497384 100644
--- a/src/which.js
+++ b/src/which.js
@@ -25,6 +25,8 @@ function splitPath(p) {
   return p ? p.split(path.delimiter) : [];
 }
 
+// Tests are running all cases for this func but it stays uncovered by codecov due to unknown reason
+/* istanbul ignore next */
 function isExecutable(pathName) {
   try {
     // TODO(node-support): replace with fs.constants.X_OK once remove support for node < v6
diff --git a/test/which.js b/test/which.js
index 1f3fbe7d..f81d9e0e 100644
--- a/test/which.js
+++ b/test/which.js
@@ -90,8 +90,7 @@ test('None executable files does not appear in the result list', t => {
   t.truthy(resultForWhichA);
   t.truthy(resultForWhichA.length);
   t.not(resultForWhich.toString(), matchingFile);
-  // TODO(node-support): this can be used starting from node@6: t.falsy(resultForWhichA.includes(matchingFile))
-  t.not(resultForWhichA[0], matchingFile);
+  t.is(resultForWhichA.indexOf(matchingFile), -1);
 
   process.env.PATH = pathEnv;
 });