diff --git a/src/main.h b/src/main.h
index bbd3d32c6..1c337d103 100644
--- a/src/main.h
+++ b/src/main.h
@@ -39,8 +39,6 @@ static const unsigned int MAX_STANDARD_TX_SIZE = 100000;
 static const unsigned int MAX_BLOCK_SIGOPS = MAX_BLOCK_SIZE/50;
 /** The maximum number of orphan transactions kept in memory */
 static const unsigned int MAX_ORPHAN_TRANSACTIONS = MAX_BLOCK_SIZE/100;
-/** The maximum number of entries in an 'inv' protocol message */
-static const unsigned int MAX_INV_SZ = 50000;
 /** The maximum size of a blk?????.dat file (since 0.8) */
 static const unsigned int MAX_BLOCKFILE_SIZE = 0x8000000; // 128 MiB
 /** The pre-allocation chunk size for blk?????.dat files (since 0.8) */
diff --git a/src/net.h b/src/net.h
index 0f4ba4f41..5a2968c3c 100644
--- a/src/net.h
+++ b/src/net.h
@@ -27,6 +27,10 @@ class CBlockIndex;
 extern int nBestHeight;
 
 
+/** The maximum number of entries in an 'inv' protocol message */
+static const unsigned int MAX_INV_SZ = 50000;
+/** The maximum number of entries in mapAskFor */
+static const size_t MAPASKFOR_MAX_SZ = MAX_INV_SZ;
 
 inline unsigned int ReceiveFloodSize() { return 1000*GetArg("-maxreceivebuffer", 5*1000); }
 inline unsigned int SendBufferSize() { return 1000*GetArg("-maxsendbuffer", 1*1000); }
@@ -357,6 +361,9 @@ public:
 
     void AskFor(const CInv& inv)
     {
+        if (mapAskFor.size() > MAPASKFOR_MAX_SZ)
+            return;
+
         // We're using mapAskFor as a priority queue,
         // the key is the earliest time the request can be sent
         int64 nRequestTime;