diff --git a/main.cpp b/main.cpp
index 10d482d898..1d9b35b534 100644
--- a/main.cpp
+++ b/main.cpp
@@ -571,10 +571,15 @@ bool CTransaction::AcceptToMemoryPool(CTxDB& txdb, bool fCheckInputs, bool* pfMi
     if ((int64)nLockTime > INT_MAX)
         return error("AcceptToMemoryPool() : not accepting nLockTime beyond 2038 yet");
 
-    // Rather not work on nonstandard transactions
-    if (!IsStandard() || GetSigOpCount() > 2 || ::GetSerializeSize(*this, SER_NETWORK) < 100)
+    // Safety limits
+    unsigned int nSize = ::GetSerializeSize(*this, SER_NETWORK);
+    if (GetSigOpCount() > 2 || nSize < 100)
         return error("AcceptToMemoryPool() : nonstandard transaction");
 
+    // Rather not work on nonstandard transactions
+    if (!IsStandard())
+        return error("AcceptToMemoryPool() : nonstandard transaction type");
+
     // Do we already have it?
     uint256 hash = GetHash();
     CRITICAL_BLOCK(cs_mapTransactions)
@@ -612,14 +617,36 @@ bool CTransaction::AcceptToMemoryPool(CTxDB& txdb, bool fCheckInputs, bool* pfMi
         }
     }
 
-    // Check against previous transactions
-    map<uint256, CTxIndex> mapUnused;
-    int64 nFees = 0;
-    if (fCheckInputs && !ConnectInputs(txdb, mapUnused, CDiskTxPos(1,1,1), pindexBest, nFees, false, false))
+    if (fCheckInputs)
     {
-        if (pfMissingInputs)
-            *pfMissingInputs = true;
-        return error("AcceptToMemoryPool() : ConnectInputs failed %s", hash.ToString().substr(0,10).c_str());
+        // Check against previous transactions
+        map<uint256, CTxIndex> mapUnused;
+        int64 nFees = 0;
+        if (!ConnectInputs(txdb, mapUnused, CDiskTxPos(1,1,1), pindexBest, nFees, false, false))
+        {
+            if (pfMissingInputs)
+                *pfMissingInputs = true;
+            return error("AcceptToMemoryPool() : ConnectInputs failed %s", hash.ToString().substr(0,10).c_str());
+        }
+
+        // Don't accept it if it can't get into a block
+        if (nFees < GetMinFee(1000))
+            return error("AcceptToMemoryPool() : not enough fees");
+
+        // Limit free transactions per 10 minutes
+        if (nFees < CENT && GetBoolArg("-limitfreerelay"))
+        {
+            static int64 nNextReset;
+            static int64 nFreeCount;
+            if (GetTime() > nNextReset)
+            {
+                nNextReset = GetTime() + 10 * 60;
+                nFreeCount = 0;
+            }
+            if (nFreeCount > 150000 && !IsFromMe())
+                return error("AcceptToMemoryPool() : free transaction rejected by rate limiter");
+            nFreeCount += nSize;
+        }
     }
 
     // Store transaction in memory
@@ -1926,7 +1953,6 @@ string GetWarnings(string strFor)
             {
                 nPriority = alert.nPriority;
                 strStatusBar = alert.strStatusBar;
-                strRPC = alert.strRPCError;
             }
         }
     }
diff --git a/main.h b/main.h
index 0b950e8074..088e2860c3 100644
--- a/main.h
+++ b/main.h
@@ -1754,7 +1754,7 @@ public:
     // Actions
     string strComment;
     string strStatusBar;
-    string strRPCError;
+    string strReserved;
 
     IMPLEMENT_SERIALIZE
     (
@@ -1772,7 +1772,7 @@ public:
 
         READWRITE(strComment);
         READWRITE(strStatusBar);
-        READWRITE(strRPCError);
+        READWRITE(strReserved);
     )
 
     void SetNull()
@@ -1790,7 +1790,7 @@ public:
 
         strComment.clear();
         strStatusBar.clear();
-        strRPCError.clear();
+        strReserved.clear();
     }
 
     string ToString() const
@@ -1815,7 +1815,6 @@ public:
                 "    nPriority    = %d\n"
                 "    strComment   = \"%s\"\n"
                 "    strStatusBar = \"%s\"\n"
-                "    strRPCError  = \"%s\"\n"
                 ")\n",
             nVersion,
             nRelayUntil,
@@ -1828,8 +1827,7 @@ public:
             strSetSubVer.c_str(),
             nPriority,
             strComment.c_str(),
-            strStatusBar.c_str(),
-            strRPCError.c_str());
+            strStatusBar.c_str());
     }
 
     void print() const
diff --git a/serialize.h b/serialize.h
index 4e90b76c03..ad9fb9faae 100644
--- a/serialize.h
+++ b/serialize.h
@@ -25,7 +25,7 @@ class CDataStream;
 class CAutoFile;
 static const unsigned int MAX_SIZE = 0x02000000;
 
-static const int VERSION = 31800;
+static const int VERSION = 31801;
 static const char* pszSubVer = "";