diff --git a/src/gridtools/MultiColvarDensity.cpp b/src/gridtools/MultiColvarDensity.cpp
index a51b83f557..c3104903fd 100644
--- a/src/gridtools/MultiColvarDensity.cpp
+++ b/src/gridtools/MultiColvarDensity.cpp
@@ -94,6 +94,8 @@ void MultiColvarDensity::registerKeywords( Keywords& keys ) {
   keys.add("compulsory","KERNEL","GAUSSIAN","the kernel function you are using.  More details on  the kernels available "
            "in plumed plumed can be found in \\ref kernelfunctions.");
   keys.add("optional","NBINS","the number of bins to use in each direction (alternative to GRID_NBIN)");
+  keys.add("optional","GRID_MIN","the lower bounds for the grid (default boxlengths)");
+  keys.add("optional","GRID_MAX","the upper bounds for the grid (default boxlengths)");
   keys.add("optional","DATA","the multicolvar which you would like to calculate the density profile for");
   keys.add("optional","ATOMS","if you are calculating a atomic density you use this keyword to specify the atoms that are involved");
   keys.addFlag("UNORMALIZED",false,"do not divide by the density");