diff --git a/src/mol-math/linear-algebra/3d/mat4.ts b/src/mol-math/linear-algebra/3d/mat4.ts
index d6ac448acb5c59d77555024d8d32fa3382aec9b9..482fc13e90157e145f8fd017cb054d465fa1935f 100644
--- a/src/mol-math/linear-algebra/3d/mat4.ts
+++ b/src/mol-math/linear-algebra/3d/mat4.ts
@@ -446,7 +446,7 @@ namespace Mat4 {
         return out
     }
 
-    export function rotate(out: Mat4, a: Mat4, rad: number, axis: Mat4) {
+    export function rotate(out: Mat4, a: Mat4, rad: number, axis: Vec3) {
         let x = axis[0], y = axis[1], z = axis[2],
             len = Math.sqrt(x * x + y * y + z * z),
             s, c, t,