diff --git a/src/mem/cache/cache.cc b/src/mem/cache/cache.cc
index 991463d76..9050a1c30 100644
--- a/src/mem/cache/cache.cc
+++ b/src/mem/cache/cache.cc
@@ -185,7 +185,11 @@ Cache::satisfyCpuSideRequest(PacketPtr pkt, CacheBlk *blk,
         if (pkt->isLLSC()) {
             blk->trackLoadLocked(pkt);
         }
+
+        // all read responses have a data payload
+        assert(pkt->hasRespData());
         pkt->setDataFromBlock(blk->data, blkSize);
+
         // determine if this read is from a (coherent) cache, or not
         // by looking at the command type; we could potentially add a
         // packet attribute such as 'FromCache' to make this check a
@@ -796,10 +800,7 @@ Cache::recvTimingReq(PacketPtr pkt)
             }
 
             pkt->makeTimingResponse();
-            // for debugging, set all the bits in the response data
-            // (also keeps valgrind from complaining when debugging settings
-            //  print out instruction results)
-            std::memset(pkt->getPtr<uint8_t>(), 0xFF, pkt->getSize());
+
             // request_time is used here, taking into account lat and the delay
             // charged if the packet comes from the xbar.
             cpuSidePort->schedTimingResp(pkt, request_time, true);
@@ -2041,7 +2042,10 @@ Cache::handleSnoop(PacketPtr pkt, CacheBlk *blk, bool is_timing,
             doTimingSupplyResponse(pkt, blk->data, is_deferred, pending_inval);
         } else {
             pkt->makeAtomicResponse();
-            pkt->setDataFromBlock(blk->data, blkSize);
+            // packets such as upgrades do not actually have any data
+            // payload
+            if (pkt->hasData())
+                pkt->setDataFromBlock(blk->data, blkSize);
         }
     }
 
diff --git a/src/mem/cache/mshr.cc b/src/mem/cache/mshr.cc
index e2141a429..1d18a2861 100644
--- a/src/mem/cache/mshr.cc
+++ b/src/mem/cache/mshr.cc
@@ -115,6 +115,9 @@ MSHR::TargetList::add(PacketPtr pkt, Tick readyTime,
 static void
 replaceUpgrade(PacketPtr pkt)
 {
+    // remember if the current packet has data allocated
+    bool has_data = pkt->hasData() || pkt->hasRespData();
+
     if (pkt->cmd == MemCmd::UpgradeReq) {
         pkt->cmd = MemCmd::ReadExReq;
         DPRINTF(Cache, "Replacing UpgradeReq with ReadExReq\n");
@@ -125,6 +128,19 @@ replaceUpgrade(PacketPtr pkt)
         pkt->cmd = MemCmd::StoreCondFailReq;
         DPRINTF(Cache, "Replacing StoreCondReq with StoreCondFailReq\n");
     }
+
+    if (!has_data) {
+        // there is no sensible way of setting the data field if the
+        // new command actually would carry data
+        assert(!pkt->hasData());
+
+        if (pkt->hasRespData()) {
+            // we went from a packet that had no data (neither request,
+            // nor response), to one that does, and therefore we need to
+            // actually allocate space for the data payload
+            pkt->allocate();
+        }
+    }
 }
 
 
diff --git a/src/mem/packet.hh b/src/mem/packet.hh
index 4614799bf..94508f697 100644
--- a/src/mem/packet.hh
+++ b/src/mem/packet.hh
@@ -508,6 +508,11 @@ class Packet : public Printable
     bool isEviction() const          { return cmd.isEviction(); }
     bool isWriteback() const         { return cmd.isWriteback(); }
     bool hasData() const             { return cmd.hasData(); }
+    bool hasRespData() const
+    {
+        MemCmd resp_cmd = cmd.responseCommand();
+        return resp_cmd.hasData();
+    }
     bool isLLSC() const              { return cmd.isLLSC(); }
     bool isError() const             { return cmd.isError(); }
     bool isPrint() const             { return cmd.isPrint(); }
@@ -1058,9 +1063,13 @@ class Packet : public Printable
     void
     allocate()
     {
-        assert(flags.noneSet(STATIC_DATA|DYNAMIC_DATA));
-        flags.set(DYNAMIC_DATA);
-        data = new uint8_t[getSize()];
+        // if either this command or the response command has a data
+        // payload, actually allocate space
+        if (hasData() || hasRespData()) {
+            assert(flags.noneSet(STATIC_DATA|DYNAMIC_DATA));
+            flags.set(DYNAMIC_DATA);
+            data = new uint8_t[getSize()];
+        }
     }
 
     /** @} */