diff --git a/R/repr_matrix_df.r b/R/repr_matrix_df.r
index fceeef9..13dcf7d 100644
--- a/R/repr_matrix_df.r
+++ b/R/repr_matrix_df.r
@@ -89,11 +89,14 @@ partition_from_parts.data.table <- function(a, part_r, part_c) {
 
 arr_partition <- function(a, rows, cols) {
 	stopifnot(rows >= 2L, cols >= 2L)
-	
+
 	# create sequences of indices to bisect rows and columns
 	part_r <- partition(nrow(a), rows)
 	part_c <- partition(ncol(a), cols)
-	
+
+	if (is.null(rownames(a))) rownames(a) <- seq_len(nrow(a))
+	if (is.null(colnames(a))) colnames(a) <- seq_len(ncol(a))
+
 	partition_from_parts(a, part_r, part_c)
 }