diff --git a/src/mem/packet.cc b/src/mem/packet.cc
index 3cd1bb9..31dc330 100644
--- a/src/mem/packet.cc
+++ b/src/mem/packet.cc
@@ -214,6 +214,10 @@
     { {IsResponse, IsError}, InvalidCmd, "InvalidDestError" },
     /* BadAddressError   -- memory address invalid */
     { {IsResponse, IsError}, InvalidCmd, "BadAddressError" },
+    /* ReadError -- packet dest unable to fulfill read command */
+    { {IsRead, IsResponse, IsError}, InvalidCmd, "ReadError" },
+    /* WriteError -- packet dest unable to fulfill write command */
+    { {IsWrite, IsResponse, IsError}, InvalidCmd, "WriteError" },
     /* FunctionalReadError */
     { {IsRead, IsResponse, IsError}, InvalidCmd, "FunctionalReadError" },
     /* FunctionalWriteError */
diff --git a/src/mem/packet.hh b/src/mem/packet.hh
index 7d32634..9238dbe 100644
--- a/src/mem/packet.hh
+++ b/src/mem/packet.hh
@@ -133,6 +133,8 @@
         // compatibility
         InvalidDestError,  // packet dest field invalid
         BadAddressError,   // memory address invalid
+        ReadError,         // packet dest unable to fulfill read command
+        WriteError,        // packet dest unable to fulfill write command
         FunctionalReadError, // unable to fulfill functional read
         FunctionalWriteError, // unable to fulfill functional write
         // Fake simulator-only commands
@@ -785,6 +787,19 @@
         cmd = MemCmd::BadAddressError;
     }
 
+    // Command error conditions. The request is sent to target but the target
+    // cannot make it.
+    void
+    setBadCommand()
+    {
+        assert(isResponse());
+        if (isWrite()) {
+            cmd = MemCmd::WriteError;
+        } else {
+            cmd = MemCmd::ReadError;
+        }
+    }
+
     void copyError(Packet *pkt) { assert(pkt->isError()); cmd = pkt->cmd; }
 
     Addr getAddr() const { assert(flags.isSet(VALID_ADDR)); return addr; }