diff --git a/source/lib/formatter.ts b/source/lib/formatter.ts
index 3a67c12..9c39327 100644
--- a/source/lib/formatter.ts
+++ b/source/lib/formatter.ts
@@ -50,7 +50,12 @@ export default (diagnostics: Diagnostic[], showDiff = false): string => {
 			}
 		}
 
-		entry.errorCount++;
+		if (diagnostic.severity === 'error') {
+			entry.errorCount++;
+		} else if (diagnostic.severity === 'warning') {
+			entry.warningCount++;
+		}
+
 		entry.messages.push(diagnostic);
 	}
 
diff --git a/source/test/cli.ts b/source/test/cli.ts
index 1f5d510..407fdf6 100644
--- a/source/test/cli.ts
+++ b/source/test/cli.ts
@@ -163,3 +163,31 @@ test('exported formatter matches cli results', async t => {
 		'1 error',
 	]);
 });
+
+test('warnings are reported correctly and do not fail', async t => {
+	const {exitCode, stdout} = await execa('../../../../cli.js', {
+		cwd: path.join(__dirname, 'fixtures/warnings/only-warnings'),
+	});
+
+	t.is(exitCode, 0);
+	verifyCli(t, stdout, [
+		'⚠  4:0  Type for expression one(1, 1) is: number',
+		'',
+		'1 warning',
+	]);
+});
+
+test('warnings are reported with errors', async t => {
+	const {exitCode, stderr} = await t.throwsAsync<ExecaError>(execa('../../../../cli.js', {
+		cwd: path.join(__dirname, 'fixtures/warnings/with-errors'),
+	}));
+
+	t.is(exitCode, 1);
+	verifyCli(t, stderr, [
+		'✖  5:19  Argument of type number is not assignable to parameter of type string.',
+		'⚠  4:0   Type for expression one(1, 1) is: number',
+		'',
+		'1 warning',
+		'1 error',
+	]);
+});
diff --git a/source/test/fixtures/warnings/only-warnings/index.d.ts b/source/test/fixtures/warnings/only-warnings/index.d.ts
new file mode 100644
index 0000000..0616eba
--- /dev/null
+++ b/source/test/fixtures/warnings/only-warnings/index.d.ts
@@ -0,0 +1,6 @@
+declare const one: {
+	(foo: string, bar: string): string;
+	(foo: number, bar: number): number;
+};
+
+export default one;
diff --git a/source/test/fixtures/warnings/only-warnings/index.js b/source/test/fixtures/warnings/only-warnings/index.js
new file mode 100644
index 0000000..f17717f
--- /dev/null
+++ b/source/test/fixtures/warnings/only-warnings/index.js
@@ -0,0 +1,3 @@
+module.exports.default = (foo, bar) => {
+	return foo + bar;
+};
diff --git a/source/test/fixtures/warnings/only-warnings/index.test-d.ts b/source/test/fixtures/warnings/only-warnings/index.test-d.ts
new file mode 100644
index 0000000..5134757
--- /dev/null
+++ b/source/test/fixtures/warnings/only-warnings/index.test-d.ts
@@ -0,0 +1,4 @@
+import {printType} from '../../../..';
+import one from '.';
+
+printType(one(1, 1));
diff --git a/source/test/fixtures/warnings/only-warnings/package.json b/source/test/fixtures/warnings/only-warnings/package.json
new file mode 100644
index 0000000..de6dc1d
--- /dev/null
+++ b/source/test/fixtures/warnings/only-warnings/package.json
@@ -0,0 +1,3 @@
+{
+	"name": "foo"
+}
diff --git a/source/test/fixtures/warnings/with-errors/index.d.ts b/source/test/fixtures/warnings/with-errors/index.d.ts
new file mode 100644
index 0000000..0616eba
--- /dev/null
+++ b/source/test/fixtures/warnings/with-errors/index.d.ts
@@ -0,0 +1,6 @@
+declare const one: {
+	(foo: string, bar: string): string;
+	(foo: number, bar: number): number;
+};
+
+export default one;
diff --git a/source/test/fixtures/warnings/with-errors/index.js b/source/test/fixtures/warnings/with-errors/index.js
new file mode 100644
index 0000000..f17717f
--- /dev/null
+++ b/source/test/fixtures/warnings/with-errors/index.js
@@ -0,0 +1,3 @@
+module.exports.default = (foo, bar) => {
+	return foo + bar;
+};
diff --git a/source/test/fixtures/warnings/with-errors/index.test-d.ts b/source/test/fixtures/warnings/with-errors/index.test-d.ts
new file mode 100644
index 0000000..65ccce6
--- /dev/null
+++ b/source/test/fixtures/warnings/with-errors/index.test-d.ts
@@ -0,0 +1,5 @@
+import {printType, expectType} from '../../../..';
+import one from '.';
+
+printType(one(1, 1));
+expectType<string>(one(1, 2));
diff --git a/source/test/fixtures/warnings/with-errors/package.json b/source/test/fixtures/warnings/with-errors/package.json
new file mode 100644
index 0000000..de6dc1d
--- /dev/null
+++ b/source/test/fixtures/warnings/with-errors/package.json
@@ -0,0 +1,3 @@
+{
+	"name": "foo"
+}