diff --git a/src/colvar/CS2Backbone.cpp b/src/colvar/CS2Backbone.cpp
index 3c228c9c78b48145a552addf10805c643661230a..d21ad75f0391937435da13a5d78a78de6d051ed5 100644
--- a/src/colvar/CS2Backbone.cpp
+++ b/src/colvar/CS2Backbone.cpp
@@ -275,7 +275,9 @@ PLUMED_COLVAR_INIT(ao)
   /* this is a workaround for those chemical shifts that can result in too large forces */
   a.remove_problematic("GLN", "CB");
   a.remove_problematic("ILE", "CB");
-  a.remove_problematic("PRO", "N");  a.remove_problematic("PRO", "H");
+  a.remove_problematic("PRO", "N");  
+  a.remove_problematic("PRO", "H");
+  a.remove_problematic("PRO", "CB");
   a.remove_problematic("GLY", "HA"); a.remove_problematic("GLY", "CB");
   /* this is a workaround for those chemical shifts that are not parameterized */
   a.remove_problematic("HIE", "HA"); a.remove_problematic("HIP", "HA"); a.remove_problematic("HSP", "HA");