diff --git a/src/include/ranges/mrange.cc.h b/src/include/ranges/mrange.cc.h
index ad93466..b352830 100644
--- a/src/include/ranges/mrange.cc.h
+++ b/src/include/ranges/mrange.cc.h
@@ -590,9 +590,9 @@ namespace CNORXZ
 		    mIPack[i]->reformat(nf,ns);
 		}
 		else {
-		    //!!!
-		    // check that format is trivial in this partition
-		    CXZ_ERROR("...");
+		    // TODO: IMPLEMENT!!!
+		    // check trivial format in this partition
+		    CXZ_ERROR("reformating with lower-dimensional formats has not yet been implemented");
 		}
 	    }, NoF {});
 	    mFormat = FormatT(nformat);
diff --git a/src/lib/ranges/yrange.cc b/src/lib/ranges/yrange.cc
index f03b956..f93fdbd 100644
--- a/src/lib/ranges/yrange.cc
+++ b/src/lib/ranges/yrange.cc
@@ -427,8 +427,9 @@ namespace CNORXZ
 	    xi *= mIs[i]->lmax().val();
 	    SizeT xj = s[j];
 	    if(xi < xj) {
+		// TODO: IMPLEMENT!!!
 		// check trivial format in this partition
-		CXZ_ERROR("...");
+		CXZ_ERROR("reformating with lower-dimensional formats has not yet been implemented");
 		continue;
 	    }
 	    j0 = j;