diff --git a/index.js b/index.js
index 99caa9a..2ba0ab3 100644
--- a/index.js
+++ b/index.js
@@ -152,10 +152,15 @@ is.typedArray = x => typedArrayTypes.has(getObjectType(x));
 
 is.inRange = (x, range) => {
 	if (is.number(range)) {
-		return (x >= Math.min(0, range)) && (x <= Math.max(range, 0));
+		return x >= Math.min(0, range) && x <= Math.max(range, 0);
 	}
 
-	return (is.array(range)) && (x >= Math.min.apply(Math, range)) && (x <= Math.max.apply(Math, range));
+	if (is.array(range) && range.length === 2) {
+		// TODO: Use spread operator here when targeting Node.js 6 or higher
+		return x >= Math.min.apply(null, range) && x <= Math.max.apply(null, range);
+	}
+
+	throw new TypeError('Invalid range');
 };
 
 module.exports = is;
diff --git a/readme.md b/readme.md
index 40e5d1b..6038e65 100644
--- a/readme.md
+++ b/readme.md
@@ -123,11 +123,22 @@ Returns `true` for instances created by a ES2015 class.
 
 ##### .inRange(value, range)
 
-Check to see if the value is within a given range, for example `is.inRange(3, [0, 5])`.
-The range supplied can be an array of any size, though this will only check for
-the minimum and maximum values in it.
+Check if `value` (number) is in the given `range`. The range is an array of two values, lower bound and upper bound, in no specific order.
+
+```js
+is.inRange(3, [0, 5]);
+is.inRange(3, [5, 0]);
+is.inRange(0, [-2, 2]);
+```
+
+##### .inRange(value, upperBound)
+
+Check if `value` (number) is in the range of `0` to `upperBound`.
+
+```js
+is.inRange(3, 10);
+```
 
-If `range` is a number (e.g., `is.inRange(3, 10)`), it will be treated as a range of 0 to `range`.
 
 ## FAQ
 
diff --git a/test.js b/test.js
index 6f5d6a6..18f6158 100644
--- a/test.js
+++ b/test.js
@@ -314,7 +314,19 @@ test('is.inRange', t => {
 	t.true(m.inRange(x, [-5, 5]));
 	t.true(m.inRange(x, [5, -5]));
 	t.false(m.inRange(x, [4, 8]));
+	t.true(m.inRange(-7, [-5, -10]));
+	t.true(m.inRange(-5, [-5, -10]));
+	t.true(m.inRange(-10, [-5, -10]));
 
 	t.true(m.inRange(x, 10));
+	t.true(m.inRange(0, 0));
 	t.false(m.inRange(x, 2));
+
+	t.throws(() => {
+		t.true(m.inRange(0));
+	});
+
+	t.throws(() => {
+		t.true(m.inRange(0, [5]));
+	});
 });