diff --git a/doc/src/PDF/colvars-refman-lammps.pdf b/doc/src/PDF/colvars-refman-lammps.pdf
index 8fcc37c26e..8b6e5bffdc 100644
Binary files a/doc/src/PDF/colvars-refman-lammps.pdf and b/doc/src/PDF/colvars-refman-lammps.pdf differ
diff --git a/lib/colvars/colvarcomp_volmaps.cpp b/lib/colvars/colvarcomp_volmaps.cpp
index 5f80e46717..865500dfeb 100644
--- a/lib/colvars/colvarcomp_volmaps.cpp
+++ b/lib/colvars/colvarcomp_volmaps.cpp
@@ -103,7 +103,7 @@ void colvar::map_total::calc_value()
 {
   colvarproxy *proxy = cvm::main()->proxy;
   int flags = is_enabled(f_cvc_gradient) ? colvarproxy::volmap_flag_gradients :
-    colvarproxy::volmap_flag_gradients;
+    colvarproxy::volmap_flag_null;
 
   if (atoms != NULL) {
     // Compute the map inside Colvars
diff --git a/lib/colvars/colvargrid.cpp b/lib/colvars/colvargrid.cpp
index 2074c97aca..b3768a47f6 100644
--- a/lib/colvars/colvargrid.cpp
+++ b/lib/colvars/colvargrid.cpp
@@ -166,6 +166,14 @@ colvar_grid_gradient::colvar_grid_gradient(std::string &filename)
   }
 
   is >> nd;
+
+  if (nd > 50) {
+    cvm::error("Error: excessive number of dimensions in file \""+
+               filename+"\".  Please ensure that the file is not corrupt.\n",
+               INPUT_ERROR);
+    return;
+  }
+
   mult = nd;
   std::vector<cvm::real> lower_in(nd), widths_in(nd);
   std::vector<int>       nx_in(nd);
diff --git a/lib/colvars/colvars_version.h b/lib/colvars/colvars_version.h
index 7847bd4aba..dd56c39f3a 100644
--- a/lib/colvars/colvars_version.h
+++ b/lib/colvars/colvars_version.h
@@ -1,3 +1,3 @@
 #ifndef COLVARS_VERSION
-#define COLVARS_VERSION "2021-08-03"
+#define COLVARS_VERSION "2021-08-06"
 #endif