diff --git a/libraries/io/eth/src/vhdl/eth_tester_rx.vhd b/libraries/io/eth/src/vhdl/eth_tester_rx.vhd
index d1c8c6fe284d33dc52ee6810338457aff7bdecd1..588f00d1e927155d2278c9b5974fc3cb68d6ff11 100644
--- a/libraries/io/eth/src/vhdl/eth_tester_rx.vhd
+++ b/libraries/io/eth/src/vhdl/eth_tester_rx.vhd
@@ -63,8 +63,8 @@ ARCHITECTURE str OF eth_tester_rx IS
   CONSTANT c_nof_total_counts     : NATURAL := 3;  -- 0 = nof_sop, 1 = nof_valid, 2 = nof_crc_corrupt
 
   CONSTANT c_empty_w              : NATURAL := 2;  -- for 0, 1, 2, 3 empty octets per word
-  CONSTANT c_fifo_fill            : NATURAL := c_eth_tester_bg_block_len_max / c_word_sz;  -- = 9000 / 4 = 2250
-  CONSTANT c_fifo_size            : NATURAL := true_log_pow2(c_fifo_fill);  -- = 4096
+  CONSTANT rx_block_sz_max        : NATURAL := c_eth_tester_rx_block_len_max / c_word_sz;  -- = 9004 / 4 = 2251
+  CONSTANT c_fifo_size            : NATURAL := true_log_pow2(rx_block_sz_max);  -- = 4096 words
 
   SIGNAL rx_udp_data         : STD_LOGIC_VECTOR(c_word_w-1 DOWNTO 0);
   SIGNAL rx_offload_sosi     : t_dp_sosi;