diff --git a/lib/JBUS/src/busmaster_async.vhd b/lib/JBUS/src/busmaster_async.vhd
index ccac16b..12ba678 100644
--- a/lib/JBUS/src/busmaster_async.vhd
+++ b/lib/JBUS/src/busmaster_async.vhd
@@ -137,7 +137,9 @@ proc_bus_read_counter:
 			elsif cmd_read_en = '1' and read_fifo_empty = '1' then
 				read_cnt <= read_cnt + 1;
 			elsif cmd_read_en = '0' and read_fifo_empty = '0' and dout_re = '1' then
-				read_cnt <= read_cnt - 1;
+				if read_cnt > 0 then
+					read_cnt <= read_cnt - 1;
+				end if;
 			end if;	
 		end if;
 	end process;