diff --git a/src-tools/lib/util/cmdline.js b/src-tools/lib/util/cmdline.js
index 7a167b19..cf115a4e 100644
--- a/src-tools/lib/util/cmdline.js
+++ b/src-tools/lib/util/cmdline.js
@@ -97,6 +97,17 @@ function addOptionValue(optSpec, opts, name, value) {
     }
 }
 
+// Check required options.
+function checkRequiredOptions(spec, opts) {
+    let options = spec.options || {};
+    for (let optName of Object.getOwnPropertyNames(options || {}).sort()) {
+        let opt = options[optName];
+        if (opt.required && !(optName in opts)) {
+            throw new TypeError('missing required option --' + optName);
+        }
+    }
+}
+
 // Parse command line given a clean argv (excluding nodejs etc) and a
 // global command/option specification object.
 function parseCommandLine(argv, argSpec) {
@@ -104,7 +115,7 @@ function parseCommandLine(argv, argSpec) {
     var command = void 0;
     var commandOpts = void 0;
     var commandPositional = [];
-    var genericSpec = argSpec.options;
+    var genericSpec = assert(argSpec);
     var commandSpec = void 0;
 
     function parseLongOption(i, t) {
@@ -232,6 +243,14 @@ function parseCommandLine(argv, argSpec) {
         }
     }
 
+    // Check required options.
+    if (genericSpec) {
+        checkRequiredOptions(genericSpec, genericOpts);
+    }
+    if (commandSpec) {
+        checkRequiredOptions(commandSpec, commandOpts);
+    }
+
     return { genericOpts, command, commandOpts, commandPositional };
 }
 exports.parseCommandLine = parseCommandLine;
diff --git a/src-tools/lib/util/fs.js b/src-tools/lib/util/fs.js
index a58f094c..d664f66a 100644
--- a/src-tools/lib/util/fs.js
+++ b/src-tools/lib/util/fs.js
@@ -61,6 +61,10 @@ function pathJoinTest() {
     // > require('path').join('foo/bar/')
     // 'foo/bar/'
 
+    if (!isDuktape()) {
+        return;
+    }
+
     assert(pathJoin('foo/bar/quux.c', '..', 'baz') === 'foo/bar/baz');
     assert(pathJoin('foo/bar/', '..', 'baz') === 'foo/baz');
     assert(pathJoin('foo/bar', '..', 'baz') === 'foo/baz');
@@ -135,6 +139,10 @@ function dirnameTest() {
     // > require('path').dirname('foo')
     // '.'
 
+    if (!isDuktape()) {
+        return;
+    }
+
     assert(dirname('foo/bar') === 'foo');
     assert(dirname('foo/bar/') === 'foo');
     assert(dirname('foo/bar//') === 'foo');
@@ -186,6 +194,10 @@ function basenameTest() {
     // > require('path').basename('foo/..')
     // '..'
 
+    if (!isDuktape()) {
+        return;
+    }
+
     assert(basename('foo') === 'foo');
     assert(basename('foo/') === 'foo');
     assert(basename('foo/bar') === 'bar');
@@ -248,6 +260,11 @@ function readFileYaml(fn) {
 }
 exports.readFileYaml = readFileYaml;
 
+function writeFileJson(fn, doc) {
+    writeFileUtf8(fn, JSON.stringify(doc) + '\n');
+}
+exports.writeFileJson = writeFileJson;
+
 function writeFileJsonPretty(fn, doc) {
     writeFileUtf8(fn, JSON.stringify(doc, null, 4) + '\n');
 }