diff --git a/src/USER-MANIFOLD/manifold_plane_wiggle.cpp b/src/USER-MANIFOLD/manifold_plane_wiggle.cpp
index fd50e774dafb08e7a3be7689ed1081e2fd3a7cef..136c52ab361a2023ee2442fc038039a8d2c1a7d0 100644
--- a/src/USER-MANIFOLD/manifold_plane_wiggle.cpp
+++ b/src/USER-MANIFOLD/manifold_plane_wiggle.cpp
@@ -24,5 +24,5 @@ void manifold_plane_wiggle::n( const double *x, double *n )
   double w = params[1];
   n[2] = 1;
   n[1] = 0.0;
-  n[0] = -a*w*cos(x[0]);
+  n[0] = -a*w*cos(w*x[0]);
 }