diff --git a/src/_impl/_angle_between_impl.scad b/src/_impl/_angle_between_impl.scad
index 4bfa9c3b..027535be 100644
--- a/src/_impl/_angle_between_impl.scad
+++ b/src/_impl/_angle_between_impl.scad
@@ -3,5 +3,5 @@ function angle_between_ccw_2d(v1, v2) =
 	a >= 0 ? a : a + 360;
 
 function angle_between_ccw_3d(v1, v2) = 
-    let(a = acos(v1 * v2 / (norm(v1) * norm(v2))))
+    let(a = acos(v1 * v2 / sqrt(v1 * v1 * v2 * v2)))
 	a >= 0 ? a : a + 360;
\ No newline at end of file