diff --git a/src/classnames.macro.js b/src/classnames.macro.js
index 45ef694..1423548 100644
--- a/src/classnames.macro.js
+++ b/src/classnames.macro.js
@@ -91,6 +91,10 @@ export default createMacro(({ babel, references: { default: paths } }) => {
       return unpackLogicalExpression(node)
     }
 
+    if (babel.types.isNullLiteral(node)) {
+      return babel.types.stringLiteral("")
+    }
+
     if (
       babel.types.isMemberExpression(node) ||
       babel.types.isIdentifier(node)
@@ -98,7 +102,11 @@ export default createMacro(({ babel, references: { default: paths } }) => {
       return babel.types.binaryExpression(
         "+",
         babel.types.stringLiteral(" "),
-        node
+        babel.types.logicalExpression(
+          "||",
+          node,
+          babel.types.stringLiteral(""),
+        )
       )
     }
 
@@ -141,6 +149,11 @@ export default createMacro(({ babel, references: { default: paths } }) => {
 
   function getValue(input) {
     const { elements } = unpackArray(input)
+    const filteredElements = elements.filter(
+      (element) => !babel.types.isNullLiteral(element)
+      && !(babel.types.isIdentifier(element) && element.name === 'undefined' )
+      && !(babel.types.isBooleanLiteral(element) && element.value === false)
+    );
 
     const values = groupBy((node) => {
       if (babel.types.isStringLiteral(node)) {
@@ -148,7 +161,7 @@ export default createMacro(({ babel, references: { default: paths } }) => {
       }
 
       return "dynamic"
-    }, elements)
+    }, filteredElements)
 
     return concatNodes([
       concatStringNodes(values.static),
diff --git a/tests/classnames.macro.test.js b/tests/classnames.macro.test.js
index 0c328f1..0fcc728 100644
--- a/tests/classnames.macro.test.js
+++ b/tests/classnames.macro.test.js
@@ -11,6 +11,22 @@ function run(code) {
   }).code.trim()
 }
 
+test("variable", (t) => {
+  const input = stripIndent`
+    import classNames from '../src/classnames.macro';
+    const something = false;
+    const CLASS_NAMES = classNames(something, "py-2");
+  `
+
+  const expected = stripIndent`
+    const something = false;
+    const CLASS_NAMES = "py-2" + (" " + (something || ""));
+  `
+
+  const output = run(input)
+  t.is(output, expected)
+})
+
 test("strings", (t) => {
   const input = stripIndent`
     import classNames from '../src/classnames.macro';
@@ -25,6 +41,48 @@ test("strings", (t) => {
   t.is(output, expected)
 })
 
+test("null", (t) => {
+  const input = stripIndent`
+    import classNames from '../src/classnames.macro';
+    const CLASS_NAMES = classNames(null);
+  `
+
+  const expected = stripIndent`
+    const CLASS_NAMES = "";
+  `
+
+  const output = run(input)
+  t.is(output, expected)
+})
+
+test("undefined", (t) => {
+  const input = stripIndent`
+    import classNames from '../src/classnames.macro';
+    const CLASS_NAMES = classNames(undefined);
+  `
+
+  const expected = stripIndent`
+    const CLASS_NAMES = "";
+  `
+
+  const output = run(input)
+  t.is(output, expected)
+})
+
+test("false", (t) => {
+  const input = stripIndent`
+    import classNames from '../src/classnames.macro';
+    const CLASS_NAMES = classNames(false);
+  `
+
+  const expected = stripIndent`
+    const CLASS_NAMES = "";
+  `
+
+  const output = run(input)
+  t.is(output, expected)
+})
+
 test("arrays", (t) => {
   const input = stripIndent`
     import classNames from '../src/classnames.macro';
@@ -82,7 +140,7 @@ test("variables", (t) => {
   `
 
   const expected = stripIndent`
-    const CLASS_NAMES = "px-1" + (" " + props.className);
+    const CLASS_NAMES = "px-1" + (" " + (props.className || ""));
   `
 
   const output = run(input)
@@ -95,12 +153,15 @@ test("mixed", (t) => {
     const CLASS_NAMES = classNames(
       props.foo && ["foo", "fighters"],
       "bar",
-      ["qux", { "baz": props.baz }, props.className]
+      undefined,
+      ["qux", { "baz": props.baz }, props.className],
+      null,
+      false
     );
   `
 
   const expected = stripIndent`
-    const CLASS_NAMES = "bar qux" + ((props.foo ? " foo fighters" : "") + ((props.baz ? " baz" : "") + (" " + props.className)));
+    const CLASS_NAMES = "bar qux" + ((props.foo ? " foo fighters" : "") + ((props.baz ? " baz" : "") + (" " + (props.className || ""))));
   `
 
   const output = run(input)