diff --git a/erasure_layout.c b/erasure_layout.c
index 56841ab32..7f3bb460d 100644
--- a/erasure_layout.c
+++ b/erasure_layout.c
@@ -189,6 +189,27 @@ static void align_region(const struct erase_layout *layout, struct flashctx *con
 	}
 }
 
+/* Deselect all the blocks from index_to_deselect and down to the smallest. */
+static void deselect_erase_functions(const struct erase_layout *layout, size_t index_to_deselect,
+					int sub_block_start, const int sub_block_end)
+{
+	for (int j = sub_block_start; j <= sub_block_end; j++)
+		layout[index_to_deselect].layout_list[j].selected = false;
+
+	int block_start_to_deselect =
+		layout[index_to_deselect].layout_list[sub_block_start].first_sub_block_index;
+	int block_end_to_deselect =
+		layout[index_to_deselect].layout_list[sub_block_end].last_sub_block_index;
+
+	if (index_to_deselect)
+		deselect_erase_functions(layout,
+					index_to_deselect - 1,
+					block_start_to_deselect,
+					block_end_to_deselect);
+	else
+		return; // index_to_deselect has already reached 0, the smallest size of block. we are done.
+}
+
 /*
  * @brief	Function to select the list of sectors that need erasing
  *
@@ -229,9 +250,17 @@ static void select_erase_functions(struct flashctx *flashctx, const struct erase
 
 		const int total_blocks = sub_block_end - sub_block_start + 1;
 		if (count == total_blocks) {
+			/* We are selecting one large block instead, so send opcode once
+			 * instead of sending many smaller ones.
+			 */
 			if (ll->start_addr >= rstart && ll->end_addr <= rend) {
-				for (int j = sub_block_start; j <= sub_block_end; j++)
-					layout[findex - 1].layout_list[j].selected = false;
+				/* Deselect all smaller blocks covering the same region. */
+				deselect_erase_functions(layout,
+							findex - 1,
+							sub_block_start,
+							sub_block_end);
+
+				/* Select large block. */
 				ll->selected = true;
 			}
 		}