diff --git a/src/mem/ruby/protocol/chi/CHI-cache-actions.sm b/src/mem/ruby/protocol/chi/CHI-cache-actions.sm
index 6123a6c70d..5d614dcc24 100644
--- a/src/mem/ruby/protocol/chi/CHI-cache-actions.sm
+++ b/src/mem/ruby/protocol/chi/CHI-cache-actions.sm
@@ -401,6 +401,12 @@ action(Initiate_Replacement, desc="") {
   }
   copyCacheAndDir(cache_entry, getDirEntry(address), tbe, initial);
 
+  // UD_RU line needs to be written back because the upstream may be in UC state.
+  if (initial == State:UD_RU) {
+    tbe.dataBlk := cache_entry.DataBlk;
+    tbe.dataBlkValid.fillMask();
+  }
+
   // model the initial tag array read
   tbe.actions.pushNB(Event:TagArrayRead);
 
@@ -1553,7 +1559,8 @@ action(Send_InvSnpResp, desc="") {
 action(Send_WriteBackOrWriteEvict, desc="") {
   assert(is_valid(tbe));
   assert(tbe.dataBlkValid.isFull());
-  assert(tbe.dataValid);
+  assert(tbe.dataValid ||
+         (tbe.dir_ownerIsExcl && tbe.dataUnique && tbe.dataDirty));
   assert(is_HN == false);
 
   assert(tbe.dataUnique || tbe.dataDirty);
@@ -1576,7 +1583,9 @@ action(Send_WriteBackOrWriteEvict, desc="") {
 action(Send_WriteCleanFull, desc="") {
   assert(is_valid(tbe));
   assert(tbe.dataBlkValid.isFull());
-  assert(tbe.dataValid);
+  // Data must be valid or the line was in UD_RU state.
+  assert(tbe.dataValid ||
+         (tbe.dir_ownerIsExcl && tbe.dataUnique && tbe.dataDirty));
   assert(is_HN == false);
   assert(tbe.dataDirty);
 
@@ -2654,14 +2663,20 @@ action(Send_WBData, desc="") {
   if (is_HN) {
     assert(tbe.dataBlkValid.isFull());
     assert(tbe.dataDirty);
-    assert(tbe.dataValid);
+    assert(tbe.dataValid ||
+           (tbe.dir_ownerIsExcl && tbe.dataUnique && tbe.dataDirty));
     tbe.snd_msgType := CHIDataType:NCBWrData;
   } else {
     if (tbe.dataValid == false) {
-      // only possible when the WB was made stale by a snoop
-      assert(tbe.is_stale);
-      tbe.dataBlkValid.fillMask();
-      tbe.snd_msgType := CHIDataType:CBWrData_I;
+      // only possible when the WB was made stale by a snoop or
+      // Writeback on UD_RU line.
+      if (tbe.dir_ownerIsExcl && tbe.dataUnique && tbe.dataDirty) {
+        tbe.snd_msgType := CHIDataType:CBWrData_UD_PD;
+      } else {
+        assert(tbe.is_stale);
+        tbe.dataBlkValid.fillMask();
+        tbe.snd_msgType := CHIDataType:CBWrData_I;
+      }
     } else if (tbe.dataUnique) {
       assert(tbe.dataBlkValid.isFull());
       if (tbe.dataDirty) {
diff --git a/src/mem/ruby/protocol/chi/CHI-cache-transitions.sm b/src/mem/ruby/protocol/chi/CHI-cache-transitions.sm
index 9aaee236ac..9ced9d1826 100644
--- a/src/mem/ruby/protocol/chi/CHI-cache-transitions.sm
+++ b/src/mem/ruby/protocol/chi/CHI-cache-transitions.sm
@@ -713,7 +713,7 @@ transition({UD_RSC, UC_RSC, SC_RSC, SD_RSC, UD, RU, RSD, RUSD, RUSC, UD_RSD, SD_
 // When in UD_RU,UC_RU,UD_RSD,SD_RSD we also just drop the line since an upstream
 // cache has an up-to-data line that it will either WriteBack or WriteEvict
 transition({SC,UC,SC_RSC,UC_RSC,
-            UD_RU,UC_RU,UD_RSD,SD_RSD}, LocalHN_Eviction, BUSY_BLKD) {ReplTBEAvailable} {
+            UC_RU,UD_RSD,SD_RSD}, LocalHN_Eviction, BUSY_BLKD) {ReplTBEAvailable} {
   Initiate_Replacement;
   Initiate_Replacement_JustDrop;
   Profile_Eviction;
@@ -722,7 +722,7 @@ transition({SC,UC,SC_RSC,UC_RSC,
   ProcessNextState;
 }
 
-transition({UD,SD,UD_RSC,SD_RSC}, LocalHN_Eviction, BUSY_BLKD) {ReplTBEAvailable} {
+transition({UD,SD,UD_RU,UD_RSC,SD_RSC}, LocalHN_Eviction, BUSY_BLKD) {ReplTBEAvailable} {
   Initiate_Replacement;
   Initiate_Replacement_WB;
   Profile_Eviction;
@@ -749,7 +749,7 @@ transition({UD,SD,UC}, Local_Eviction, BUSY_BLKD) {ReplTBEAvailable} {
   ProcessNextState;
 }
 
-transition({UD_RU,UC_RU,UD_RSD,SD_RSD,SC_RSC,UC_RSC}, Local_Eviction, BUSY_BLKD) {ReplTBEAvailable} {
+transition({UC_RU,UD_RSD,SD_RSD,SC_RSC,UC_RSC}, Local_Eviction, BUSY_BLKD) {ReplTBEAvailable} {
   Initiate_Replacement;
   Initiate_Replacement_JustDrop;
   Profile_Eviction;
@@ -758,7 +758,7 @@ transition({UD_RU,UC_RU,UD_RSD,SD_RSD,SC_RSC,UC_RSC}, Local_Eviction, BUSY_BLKD)
   ProcessNextState;
 }
 
-transition({UD_RSC,SD_RSC}, Local_Eviction, BUSY_BLKD) {ReplTBEAvailable} {
+transition({UD_RU, UD_RSC,SD_RSC}, Local_Eviction, BUSY_BLKD) {ReplTBEAvailable} {
   Initiate_Replacement;
   Initiate_Replacement_WB;
   Profile_Eviction;