diff --git a/src/compute_msd_chunk.cpp b/src/compute_msd_chunk.cpp
index ee167a953d..317b601bc3 100644
--- a/src/compute_msd_chunk.cpp
+++ b/src/compute_msd_chunk.cpp
@@ -119,6 +119,7 @@ void ComputeMSDChunk::compute_array()
   if (firstflag) {
     nchunk = n;
     allocate();
+    size_array_rows = nchunk;
   } else if (n != nchunk) 
     error->all(FLERR,"Compute msd/chunk nchunk is not static");