diff --git a/vunit/vhdl/verification_components/run.py b/vunit/vhdl/verification_components/run.py
index 4033e484f6..8dee0b51ea 100644
--- a/vunit/vhdl/verification_components/run.py
+++ b/vunit/vhdl/verification_components/run.py
@@ -144,7 +144,7 @@ def gen_avalon_master_tests(obj, *args):
 
 TB_AXI_STREAM_PROTOCOL_CHECKER = LIB.test_bench("tb_axi_stream_protocol_checker")
 
-for data_length in [0, 8]:
+for data_length in [0, 8, 32]:
     for test in TB_AXI_STREAM_PROTOCOL_CHECKER.get_tests("*passing*tdata*"):
         test.add_config(name="data_length=%d" % data_length, generics=dict(data_length=data_length))
 
diff --git a/vunit/vhdl/verification_components/test/tb_axi_stream_protocol_checker.vhd b/vunit/vhdl/verification_components/test/tb_axi_stream_protocol_checker.vhd
index 092151b25d..1057314c65 100644
--- a/vunit/vhdl/verification_components/test/tb_axi_stream_protocol_checker.vhd
+++ b/vunit/vhdl/verification_components/test/tb_axi_stream_protocol_checker.vhd
@@ -42,7 +42,7 @@ architecture a of tb_axi_stream_protocol_checker is
   constant logger           : logger_t                      := get_logger("protocol_checker");
   constant protocol_checker : axi_stream_protocol_checker_t := new_axi_stream_protocol_checker(
     data_length => tdata'length, id_length => tid'length, dest_length => tdest'length, user_length => tuser'length,
-    logger => logger, actor => new_actor("protocol_checker"), max_waits => max_waits
+    logger => logger, actor => new_actor("protocol_checker"), max_waits => max_waits, allow_x_in_null_bytes => true
   );
   constant meta_values      : std_logic_vector(1 to 5)      := "-XWZU";
   constant valid_values     : std_logic_vector(1 to 4)      := "01LH";
@@ -168,6 +168,29 @@ begin
       end loop;
     end;
 
+    procedure pass_masked_unknown_test(
+      signal d, k, s : out std_logic_vector;
+      signal e1, e2 : out std_logic) is
+    begin
+      wait until rising_edge(aclk);
+      e1 <= '1';
+      e2 <= '1';
+
+      for i in valid_values'range loop
+        for j in k'range loop
+          for l in meta_values'range loop
+            k <= (k'range => '1');
+            s  <= (s'range => '1');
+            k(j) <= '0';
+            s(j) <= '0';
+            d <= (d'range => valid_values(i));
+            d(j*8+7 downto j*8) <= (others => meta_values(l));
+            wait until rising_edge(aclk);
+          end loop;
+        end loop;
+      end loop;
+    end;
+
     procedure fail_unknown_test(
       signal d: out std_logic_vector;
       signal e1, e2: out std_logic;
@@ -315,6 +338,9 @@ begin
     elsif run("Test passing check of that tdata must not be unknown when tvalid is high") then
       pass_unknown_test(tdata, tvalid, tready);
 
+    elsif run("Test passing check of that valid tdata bytes must not be unknown when tvalid is high") then
+      pass_masked_unknown_test(tdata, tkeep, tstrb, tvalid, tready);
+
     elsif run("Test failing check of that tdata must not be unknown when tvalid is high") then
       fail_unknown_test(tdata, tvalid, tready, ":rule 5", "tdata", "tvalid");