diff --git a/src/math/p5.Vector.js b/src/math/p5.Vector.js
index d2dd4abef5..703cfa6cda 100644
--- a/src/math/p5.Vector.js
+++ b/src/math/p5.Vector.js
@@ -2972,8 +2972,8 @@ p5.Vector = class {
  * </div>
  */
   reflect(surfaceNormal) {
-    surfaceNormal.normalize();
-    return this.sub(surfaceNormal.mult(2 * this.dot(surfaceNormal)));
+    const surfaceNormalCopy = p5.Vector.normalize(surfaceNormal);
+    return this.sub(surfaceNormalCopy.mult(2 * this.dot(surfaceNormalCopy)));
   }
 
   /**
diff --git a/test/unit/math/p5.Vector.js b/test/unit/math/p5.Vector.js
index 07a7d6b454..ef3570ee0b 100644
--- a/test/unit/math/p5.Vector.js
+++ b/test/unit/math/p5.Vector.js
@@ -1646,6 +1646,21 @@ suite('p5.Vector', function() {
           0.01
         );
       });
+      test('should not update surface normal', function() {
+        const tolerance = 0.001;
+        assert.closeTo(x_normal.x, 3, tolerance);
+        assert.closeTo(x_normal.y, 0, tolerance);
+        assert.closeTo(x_normal.z, 0, tolerance);
+
+        assert.closeTo(y_normal.x, 0, tolerance);
+        assert.closeTo(y_normal.y, 3, tolerance);
+        assert.closeTo(y_normal.z, 0, tolerance);
+
+        assert.closeTo(z_normal.x, 0, tolerance);
+        assert.closeTo(z_normal.y, 0, tolerance);
+        assert.closeTo(z_normal.z, 3, tolerance);
+      });
+
     });
 
     suite('p5.Vector.reflect() [CLASS]', function() {
@@ -1696,6 +1711,22 @@ suite('p5.Vector', function() {
         expect(z_bounce_incoming).to.not.equal(z_bounce_outgoing);
       });
 
+      test('should not update surface normal', function() {
+        const tolerance = 0.001;
+        assert.closeTo(x_normal.x, 3, tolerance);
+        assert.closeTo(x_normal.y, 0, tolerance);
+        assert.closeTo(x_normal.z, 0, tolerance);
+
+        assert.closeTo(y_normal.x, 0, tolerance);
+        assert.closeTo(y_normal.y, 3, tolerance);
+        assert.closeTo(y_normal.z, 0, tolerance);
+
+        assert.closeTo(z_normal.x, 0, tolerance);
+        assert.closeTo(z_normal.y, 0, tolerance);
+        assert.closeTo(z_normal.z, 3, tolerance);
+      });
+
+
       test('should update target', function() {
         assert.equal(x_target, x_bounce_outgoing);
         assert.equal(y_target, y_bounce_outgoing);