diff --git a/lib/stringify.js b/lib/stringify.js
index d34dbe15..fb53ca07 100644
--- a/lib/stringify.js
+++ b/lib/stringify.js
@@ -79,7 +79,7 @@ var stringify = function stringify( // eslint-disable-line func-name-matching
     }
 
     var objKeys;
-    if (Array.isArray(filter)) {
+    if (isArray(filter)) {
         objKeys = filter;
     } else {
         var keys = Object.keys(obj);
@@ -93,7 +93,7 @@ var stringify = function stringify( // eslint-disable-line func-name-matching
             continue;
         }
 
-        if (Array.isArray(obj)) {
+        if (isArray(obj)) {
             pushToArray(values, stringify(
                 obj[key],
                 generateArrayPrefix(prefix, key),
@@ -158,7 +158,7 @@ module.exports = function (object, opts) {
     if (typeof options.filter === 'function') {
         filter = options.filter;
         obj = filter('', obj);
-    } else if (Array.isArray(options.filter)) {
+    } else if (isArray(options.filter)) {
         filter = options.filter;
         objKeys = filter;
     }
diff --git a/test/stringify.js b/test/stringify.js
index 1c2a2237..5d18d230 100644
--- a/test/stringify.js
+++ b/test/stringify.js
@@ -19,6 +19,15 @@ test('stringify()', function (t) {
         st.end();
     });
 
+    t.test('stringifies falsy values', function (st) {
+        st.equal(qs.stringify(undefined), '');
+        st.equal(qs.stringify(null), '');
+        st.equal(qs.stringify(null, { strictNullHandling: true }), '');
+        st.equal(qs.stringify(false), '');
+        st.equal(qs.stringify(0), '');
+        st.end();
+    });
+
     t.test('adds query prefix', function (st) {
         st.equal(qs.stringify({ a: 'b' }, { addQueryPrefix: true }), '?a=b');
         st.end();
@@ -29,6 +38,13 @@ test('stringify()', function (t) {
         st.end();
     });
 
+    t.test('stringifies nested falsy values', function (st) {
+        st.equal(qs.stringify({ a: { b: { c: null } } }), 'a%5Bb%5D%5Bc%5D=');
+        st.equal(qs.stringify({ a: { b: { c: null } } }, { strictNullHandling: true }), 'a%5Bb%5D%5Bc%5D');
+        st.equal(qs.stringify({ a: { b: { c: false } } }), 'a%5Bb%5D%5Bc%5D=false');
+        st.end();
+    });
+
     t.test('stringifies a nested object', function (st) {
         st.equal(qs.stringify({ a: { b: 'c' } }), 'a%5Bb%5D=c');
         st.equal(qs.stringify({ a: { b: { c: { d: 'e' } } } }), 'a%5Bb%5D%5Bc%5D%5Bd%5D=e');