diff -r 568e9a533cf0 -r a6a57181b1bd src/mem/mem_checker.cc
--- a/src/mem/mem_checker.cc	Tue Feb 03 20:05:56 2015 +0000
+++ b/src/mem/mem_checker.cc	Tue Feb 03 20:06:08 2015 +0000
@@ -195,6 +195,17 @@
         }
         // Record non-matching, but possible value
         _lastExpectedData.push_back(last_obs.data);
+    } else {
+        // We have not seen any valid observation, and the only writes
+        // observed are overlapping, so anything (in particular the
+        // initialisation value) goes
+        // NOTE: We can overlap with multiple write clusters, here
+        if (!writeClusters.empty() && wc_overlap) {
+            // ensure that all write clusters really overlap this read
+            assert(writeClusters.begin()->start < complete &&
+                   writeClusters.rbegin()->complete > start);
+            return true;
+        }
     }
 
     if (_lastExpectedData.empty()) {