diff --git a/src/TODO.txt b/src/TODO.txt
index ace75d0..a886950 100644
--- a/src/TODO.txt
+++ b/src/TODO.txt
@@ -99,6 +99,7 @@
     ros2 run rosidl_adapter msg2idl.py *.msg
     ros2 run rosidl_adapter srv2idl.py *.srv
 * The publication_handle of the DDS Specification (e.g. the one returned in the Sample Info) is an implementation specific ID that can identify local and remote DDS Entities LOCALY.
+* Testbench did not catch Bug, where the Pub ACKNACK was sent to as Sub ACKNACK (ACKNACK Destinations were flipped). Extend testbench to catch this case.
 
 * Fast-RTPS does not follow DDSI-RTPS Specification
     - Open Github Issue
diff --git a/src/Tests/Level_1/L1_rtps_discovery_module_test1.vhd b/src/Tests/Level_1/L1_rtps_discovery_module_test1.vhd
index d8bb22d..a29886e 100644
--- a/src/Tests/Level_1/L1_rtps_discovery_module_test1.vhd
+++ b/src/Tests/Level_1/L1_rtps_discovery_module_test1.vhd
@@ -131,8 +131,8 @@ architecture testbench of L1_rtps_discovery_module_test1 is
         -- PUBLISHER ACKNACK
         sub                         := DEFAULT_RTPS_SUBMESSAGE;
         sub.submessageID            := SID_ACKNACK;
-        sub.writerId                := ENTITYID_SEDP_BUILTIN_SUBSCRIPTIONS_ANNOUNCER;
-        sub.readerId                := ENTITYID_SEDP_BUILTIN_SUBSCRIPTIONS_DETECTOR;
+        sub.writerId                := ENTITYID_SEDP_BUILTIN_PUBLICATIONS_ANNOUNCER;
+        sub.readerId                := ENTITYID_SEDP_BUILTIN_PUBLICATIONS_DETECTOR;
         sub.readerSNState.base      := pub_sn;
         sub.readerSNState.numBits   := int(WORD_WIDTH, CDR_LONG_WIDTH);
         sub.readerSNState.bitmap    := (0 to WORD_WIDTH-1 => '1', others => '0');
@@ -142,8 +142,8 @@ architecture testbench of L1_rtps_discovery_module_test1 is
         -- SUBSCRIBER ACKNACK
         sub                         := DEFAULT_RTPS_SUBMESSAGE;
         sub.submessageID            := SID_ACKNACK;
-        sub.writerId                := ENTITYID_SEDP_BUILTIN_PUBLICATIONS_ANNOUNCER;
-        sub.readerId                := ENTITYID_SEDP_BUILTIN_PUBLICATIONS_DETECTOR;
+        sub.writerId                := ENTITYID_SEDP_BUILTIN_SUBSCRIPTIONS_ANNOUNCER;
+        sub.readerId                := ENTITYID_SEDP_BUILTIN_SUBSCRIPTIONS_DETECTOR;
         sub.readerSNState.base      := sub_sn;
         sub.readerSNState.numBits   := int(WORD_WIDTH, CDR_LONG_WIDTH);
         sub.readerSNState.bitmap    := (0 to WORD_WIDTH-1 => '1', others => '0');
diff --git a/src/rtps_discovery_module.vhd b/src/rtps_discovery_module.vhd
index ab50cc2..7ee1743 100644
--- a/src/rtps_discovery_module.vhd
+++ b/src/rtps_discovery_module.vhd
@@ -3358,11 +3358,11 @@ begin
                                 cnt_next        <= cnt + 1;
                             -- Reader Entity ID
                             when 1 =>
-                                data_out_sig    <= ENTITYID_SEDP_BUILTIN_SUBSCRIPTIONS_DETECTOR;
+                                data_out_sig    <= ENTITYID_SEDP_BUILTIN_PUBLICATIONS_DETECTOR;
                                 cnt_next        <= cnt + 1;
                             -- Writer Entity ID
                             when 2 =>
-                                data_out_sig    <= ENTITYID_SEDP_BUILTIN_SUBSCRIPTIONS_ANNOUNCER;
+                                data_out_sig    <= ENTITYID_SEDP_BUILTIN_PUBLICATIONS_ANNOUNCER;
                                 cnt_next        <= cnt + 1;
                             -- Sequence Number Set (Bitmap Base 1/2)
                             when 3 =>
@@ -3393,11 +3393,11 @@ begin
                                 cnt_next        <= cnt + 1;
                             -- Reader Entity ID
                             when 9 =>
-                                data_out_sig    <= ENTITYID_SEDP_BUILTIN_PUBLICATIONS_DETECTOR;
+                                data_out_sig    <= ENTITYID_SEDP_BUILTIN_SUBSCRIPTIONS_DETECTOR;
                                 cnt_next        <= cnt + 1;
                             -- Writer Entity ID
                             when 10 =>
-                                data_out_sig    <= ENTITYID_SEDP_BUILTIN_PUBLICATIONS_ANNOUNCER;
+                                data_out_sig    <= ENTITYID_SEDP_BUILTIN_SUBSCRIPTIONS_ANNOUNCER;
                                 cnt_next        <= cnt + 1;
                             -- Sequence Number Set (Bitmap Base 1/2)
                             when 11 =>