diff --git a/fslascii2img.cc b/fslascii2img.cc
index 400db5f1367c791e485b8683f6b515e9cc3e4917..42854eba2e9dacda36d4ce6cf33937dffaa22df0 100644
--- a/fslascii2img.cc
+++ b/fslascii2img.cc
@@ -37,6 +37,7 @@ int do_work(int argc, char *argv[])
   amat = read_ascii_matrix(input_name);
   if (xsize*ysize*zsize*tsize != amat.Nrows() * amat.Ncols()) {
     cerr << "Sizes incompatible: " <<  xsize*ysize*zsize*tsize << " voxels vs " << amat.Nrows() * amat.Ncols() << " numbers" << endl;
+    cerr << "Matrix dimensions are " << amat.Nrows() << " by " << amat.Ncols() << endl;
     exit(EXIT_FAILURE);
   }
   amat = reshape(amat.t(),tsize,xsize*ysize*zsize);