diff --git a/src/main.cpp b/src/main.cpp
index 082456af..88686df6 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -5452,6 +5452,7 @@ bool SendMessages(CNode* pto, bool fSendTrickle)
                     vGetData.clear();
                 }
             }
+            pto->setAskFor.erase(inv.hash);
             pto->mapAskFor.erase(pto->mapAskFor.begin());
         }
         if (!vGetData.empty())
diff --git a/src/net.cpp b/src/net.cpp
index 04e48ac6..710e6167 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -2180,6 +2180,10 @@ void CNode::AskFor(const CInv& inv)
 {
     if (mapAskFor.size() > MAPASKFOR_MAX_SZ)
         return;
+    // a peer may not occupy multiple positions in an inv's request queue
+    if (!setAskFor.insert(inv.hash).second)
+        return;
+
     // We're using mapAskFor as a priority queue,
     // the key is the earliest time the request can be sent
     int64_t nRequestTime;
diff --git a/src/net.h b/src/net.h
index 66f733e0..bc6ab291 100644
--- a/src/net.h
+++ b/src/net.h
@@ -310,6 +310,7 @@ public:
     mruset<CInv> setInventoryKnown;
     std::vector<CInv> vInventoryToSend;
     CCriticalSection cs_inventory;
+    std::set<uint256> setAskFor;
     std::multimap<int64_t, CInv> mapAskFor;
 
     // Ping time measurement: