diff --git a/src/fix_wall_region.cpp b/src/fix_wall_region.cpp
index 8b1fc6c166..9c7cb70648 100644
--- a/src/fix_wall_region.cpp
+++ b/src/fix_wall_region.cpp
@@ -367,6 +367,7 @@ void FixWallRegion::colloid(double r, double rad)
 
 void FixWallRegion::harmonic(double r)
 {
-  fwall = 2.0*epsilon*r;
-  eng = epsilon*r*r;
+  double dr = cutoff - r;
+  fwall = 2.0*epsilon*dr;
+  eng = epsilon*dr*dr;
 }