diff --git a/examples/friction/in.friction b/examples/friction/in.friction
index 3522e065c8..56d3080544 100644
--- a/examples/friction/in.friction
+++ b/examples/friction/in.friction
@@ -69,6 +69,7 @@ fix		1 all nve
 fix		2 boundary setforce 0.0 0.0 0.0
 fix		3 mobile temp/rescale 200 0.1 0.1 0.02 1.0
 fix_modify	3 temp new
+fix             4 all enforce2d
 
 # Run