diff --git a/main.js b/main.js
index d3b5e244..cf8657ed 100755
--- a/main.js
+++ b/main.js
@@ -114,6 +114,24 @@ updateNotifier({pkg: cli.pkg}).notify();
 
 const {input, flags: opts} = cli;
 
+// Make data types for `opts.space` match those of the API
+// Check for string type because `xo --no-space` sets `opts.space` to `false`
+if (typeof opts.space === 'string') {
+	if (/^\d+$/.test(opts.space)) {
+		opts.space = parseInt(opts.space, 10);
+	} else if (opts.space === 'true') {
+		opts.space = true;
+	} else if (opts.space === 'false') {
+		opts.space = false;
+	} else {
+		if (opts.space !== '') {
+			// Assume `opts.space` was set to a filename when run as `xo --space file.js`
+			input.push(opts.space);
+		}
+		opts.space = true;
+	}
+}
+
 const log = report => {
 	const reporter = opts.reporter ? xo.getFormatter(opts.reporter) : formatterPretty;
 
diff --git a/test/fixtures/space/one-space.js b/test/fixtures/space/one-space.js
new file mode 100644
index 00000000..0b1b5e7d
--- /dev/null
+++ b/test/fixtures/space/one-space.js
@@ -0,0 +1,3 @@
+console.log([
+ 1
+]);
diff --git a/test/fixtures/space/two-spaces.js b/test/fixtures/space/two-spaces.js
new file mode 100644
index 00000000..baa2c240
--- /dev/null
+++ b/test/fixtures/space/two-spaces.js
@@ -0,0 +1,3 @@
+console.log([
+  1
+]);
diff --git a/test/main.js b/test/main.js
index 07b6a5a1..b55ab082 100644
--- a/test/main.js
+++ b/test/main.js
@@ -115,3 +115,38 @@ test('cli option takes precedence over config', async t => {
 	// i.e make sure absent cli flags are not parsed as `false`
 	await t.throws(main(['--stdin'], {input}));
 });
+
+test('space option with number value', async t => {
+	const cwd = path.join(__dirname, 'fixtures/space');
+	const {stdout} = await t.throws(main(['--space=4', 'one-space.js'], {cwd}));
+	t.true(stdout.includes('Expected indentation of 4 spaces'));
+});
+
+test('space option as boolean', async t => {
+	const cwd = path.join(__dirname, 'fixtures/space');
+	const {stdout} = await t.throws(main(['--space'], {cwd}));
+	t.true(stdout.includes('Expected indentation of 2 spaces'));
+});
+
+test('space option as boolean with filename', async t => {
+	const cwd = path.join(__dirname, 'fixtures/space');
+	const {stdout} = await main(['--reporter=json', '--space', 'two-spaces.js'], {
+		cwd,
+		reject: false
+	});
+	const reports = JSON.parse(stdout);
+
+	// Only the specified file was checked (filename was not the value of `space`)
+	t.is(reports.length, 1);
+
+	// The default space value of 2 was expected
+	t.is(reports[0].errorCount, 0);
+});
+
+test('space option with boolean strings', async t => {
+	const cwd = path.join(__dirname, 'fixtures/space');
+	const trueResult = await t.throws(main(['--space=true'], {cwd}));
+	const falseResult = await t.throws(main(['--space=false'], {cwd}));
+	t.true(trueResult.stdout.includes('Expected indentation of 2 spaces'));
+	t.true(falseResult.stdout.includes('Expected indentation of 1 tab'));
+});