diff --git a/binaries/data/mods/public/globalscripts/vector.js b/binaries/data/mods/public/globalscripts/vector.js
index 3a404135d4..5d10e4c5b5 100644
--- a/binaries/data/mods/public/globalscripts/vector.js
+++ b/binaries/data/mods/public/globalscripts/vector.js
@@ -77,7 +77,7 @@ Vector2D.prototype.rotate = function(angle)
 
 	return this.set(
 		this.x * cos + this.y * sin,
-		this.y * cos - this.x * sin);
+		-this.x * sin + this.y * cos);
 };
 
 /**
diff --git a/binaries/data/mods/public/simulation/components/tests/test_Vector.js b/binaries/data/mods/public/simulation/components/tests/test_Vector.js
index 92f1f7876b..8ae3e6b715 100644
--- a/binaries/data/mods/public/simulation/components/tests/test_Vector.js
+++ b/binaries/data/mods/public/simulation/components/tests/test_Vector.js
@@ -74,6 +74,21 @@ var brokenVector = {
 	}
 }
 
+// Test Vector2D rotation further
+{
+	let epsilon = 0.00000001;
+
+	for (let i = 0; i <= 128; ++i)
+	{
+		let angle = i / 128 * Math.PI;
+		let vec1 = new Vector2D(Math.cos(angle), Math.sin(angle));
+		let vec2 = new Vector2D(1, 0).rotate(-angle);
+
+		TS_ASSERT_EQUALS_APPROX(vec1.x, vec2.x, epsilon);
+		TS_ASSERT_EQUALS_APPROX(vec1.y, vec2.y, epsilon);
+	}
+}
+
 // Test Vector2D rotation around a center
 {
 	let epsilon = 0.00000001;
diff --git a/binaries/data/tests/test_setup.js b/binaries/data/tests/test_setup.js
index 94d1980b14..f4c0f78cfd 100644
--- a/binaries/data/tests/test_setup.js
+++ b/binaries/data/tests/test_setup.js
@@ -34,6 +34,9 @@ global.TS_ASSERT_EQUALS = function TS_ASSERT_EQUALS(x, y)
 
 global.TS_ASSERT_EQUALS_APPROX = function TS_ASSERT_EQUALS_APPROX(x, y, maxDifference)
 {
+	if (!Number.isInteger(maxDifference))
+		fail("Test must pass a maximum difference!");
+
 	if (Math.abs(x - y) > maxDifference)
 		fail("Expected almost equal, got " + uneval(x) + " !== " + uneval(y));
 }