--- a/xpcom/base/nsMemoryReporterManager.cpp
+++ b/xpcom/base/nsMemoryReporterManager.cpp
@@ -1049,19 +1049,40 @@ DMDVCheckAndDump()
     // Do vanilla reporters.
     nsCOMPtr<nsISimpleEnumerator> e;
     mgr->EnumerateReporters(getter_AddRefs(e));
     bool more;
     while (NS_SUCCEEDED(e->HasMoreElements(&more)) && more) {
         nsCOMPtr<nsIMemoryReporter> r;
         e->GetNext(getter_AddRefs(r));
 
-        // Just getting the amount is enough for the reporter to report to DMDV.
-        int64_t amount;
-        (void)r->GetAmount(&amount);
+        int32_t kind;
+        nsresult rv = r->GetKind(&kind);
+        if (NS_FAILED(rv)) {
+            continue;
+        }
+        nsCString path;
+        rv = r->GetPath(path);
+        if (NS_FAILED(rv)) {
+            continue;
+        }
+
+        // We're only interested in HEAP explicit reporters.  (In particular,
+        // some heap blocks are deliberately measured once inside an "explicit"
+        // reporter and once outside, which isn't a problem.  This condition
+        // prevents them being reported as double-counted.  See bug 811018
+        // comment 2.)
+        if (kind == nsIMemoryReporter::KIND_HEAP &&
+            path.Find("explicit") == 0)
+        {
+            // Just getting the amount is enough for the reporter to report to
+            // DMDV.
+            int64_t amount;
+            (void)r->GetAmount(&amount);
+        }
     }
 
     // Do multi-reporters.
     nsCOMPtr<nsISimpleEnumerator> e2;
     mgr->EnumerateMultiReporters(getter_AddRefs(e2));
     nsRefPtr<NullMultiReporterCallback> cb = new NullMultiReporterCallback();
     while (NS_SUCCEEDED(e2->HasMoreElements(&more)) && more) {
       nsCOMPtr<nsIMemoryMultiReporter> r;