diff --git a/lib/colvars/colvar.cpp b/lib/colvars/colvar.cpp
index 25ffec8986..6adb8f84dd 100644
--- a/lib/colvars/colvar.cpp
+++ b/lib/colvars/colvar.cpp
@@ -167,6 +167,9 @@ colvar::colvar (std::string const &conf)
   // check the available features of each cvc
   for (size_t i = 0; i < cvcs.size(); i++) {
 
+    if ((cvcs[i])->b_debug_gradients)
+      enable (task_gradients);
+
     if ((cvcs[i])->sup_np != 1) {
       if (cvm::debug() && b_linear)
         cvm::log ("Warning: You are using a non-linear polynomial "
diff --git a/lib/colvars/colvarmodule.h b/lib/colvars/colvarmodule.h
index 997b0ea1b3..e1b39f7c33 100644
--- a/lib/colvars/colvarmodule.h
+++ b/lib/colvars/colvarmodule.h
@@ -2,7 +2,7 @@
 #define COLVARMODULE_H
 
 #ifndef COLVARS_VERSION
-#define COLVARS_VERSION "2013-06-07"
+#define COLVARS_VERSION "2013-06-10"
 #endif
 
 #ifndef COLVARS_DEBUG
diff --git a/src/USER-COLVARS/colvarproxy_lammps.cpp b/src/USER-COLVARS/colvarproxy_lammps.cpp
index 7019db3858..159b8a554f 100644
--- a/src/USER-COLVARS/colvarproxy_lammps.cpp
+++ b/src/USER-COLVARS/colvarproxy_lammps.cpp
@@ -155,7 +155,7 @@ double colvarproxy_lammps::compute()
   }
 
   // zero the forces on the atoms, so that they can be accumulated by the colvars
-  for (size_t i = 0; i < colvars_atoms.size(); i++) {
+  for (size_t i = 0; i < applied_forces.size(); i++) {
     applied_forces[i].x = applied_forces[i].y = applied_forces[i].z = 0.0;
   }