diff --git a/src/darksend.cpp b/src/darksend.cpp
index 3bf9bceaea..0bfc0dfc2e 100644
--- a/src/darksend.cpp
+++ b/src/darksend.cpp
@@ -227,10 +227,35 @@ void CDarkSendPool::Check()
 // until the transaction is either complete or fails. 
 //
 void CDarkSendPool::ChargeFees(){
-    return;
     
     if(fMasterNode) {
         int i = 0;
+
+        BOOST_FOREACH(const CTransaction& txCollateral, vecSessionCollateral) {
+            bool found = false;
+            BOOST_FOREACH(const CDarkSendEntry v, entries) {
+                if(v.collateral == txCollateral) found = false;
+            }
+
+            // This queue entry didn't send us the promised transaction
+            if(!found){
+                LogPrintf("CDarkSendPool::ChargeFees -- found uncooperative node (didn't send transaction). charging fees. %u\n", i);
+
+                CWalletTx wtxCollateral = CWalletTx(pwalletMain, txCollateral);
+
+                // Broadcast
+                if (!wtxCollateral.AcceptToMemoryPool(true, false))
+                {
+                    // This must not fail. The transaction has already been signed and recorded.
+                    LogPrintf("CDarkSendPool::ChargeFees() : Error: Transaction not valid");
+                }
+                wtxCollateral.RelayWalletTransaction();
+            }
+            i++;
+        }
+
+        i = 0;
+
         // who didn't sign?
         BOOST_FOREACH(const CDarkSendEntry v, entries) {
             BOOST_FOREACH(const CDarkSendEntryVin s, v.sev) {
@@ -396,6 +421,12 @@ bool CDarkSendPool::IsCollateralValid(const CTransaction& txCollateral){
         if(fDebug) LogPrintf ("CDarkSendPool::IsCollateralValid - not correct amount or addr (0)\n");
         return false;
     }
+    //collateral transactions are required to have abnormally large fees associated, to make double
+    //spending very expensive.
+    if(txCollateral.GetValueOut() < DARKSEND_COLLATERAL*2) {
+        if(fDebug) LogPrintf ("CDarkSendPool::IsCollateralValid - did not include enough fees in transaction\n");
+        return false;
+    }
 
     LogPrintf("CDarkSendPool::IsCollateralValid %s\n", txCollateral.ToString().c_str());
 
@@ -1743,6 +1774,7 @@ bool CDarkSendPool::IsCompatibleWithSession(int64 nAmount, CTransaction txCollat
 
     sessionUsers++;
     lastTimeChanged = GetTimeMillis();
+    vecSessionCollateral.push_back(txCollateral);
 
     return true;
 }
diff --git a/src/darksend.h b/src/darksend.h
index bd315c7ce2..a77a0ab707 100644
--- a/src/darksend.h
+++ b/src/darksend.h
@@ -26,7 +26,7 @@ extern std::string strMasterNodePrivKey;
 extern std::vector<CDarksendQueue> vecDarksendQueue;
 extern std::vector<CTxIn> vecMasternodeAskedFor;
 
-static const int64 DARKSEND_COLLATERAL = 0.025*COIN;
+static const int64 DARKSEND_COLLATERAL = 0.0125*COIN;
 static const int64 DARKSEND_FEE = 0.0125*COIN;
 
 
@@ -312,6 +312,7 @@ public:
     int sessionUsers; //N Users have said they'll join
     bool sessionFoundMasternode; //If we've found a compatible masternode
     int sessionTries;
+    std::vector<CTransaction> vecSessionCollateral;
 
     int lastSplitUpBlock;
     int splitUpInARow; // how many splits we've done since a success?
diff --git a/src/wallet.cpp b/src/wallet.cpp
index 8932ea137f..00271aa9f2 100644
--- a/src/wallet.cpp
+++ b/src/wallet.cpp
@@ -1772,7 +1772,12 @@ int64 CWallet::GetTotalValue(std::vector<CTxIn> vCoins) {
 
 bool CWallet::CreateCollateralTransaction(CTransaction& txCollateral, std::string strReason)
 {
-    int64 nFeeRet = 0.001*COIN; ///need to get a better fee calc
+    /*
+        To doublespend a collateral transaction, it will require a fee higher than this. So there's 
+        still a significant cost. 
+    */
+    int64 nFeeRet = DARKSEND_COLLATERAL;
+
     CReserveKey reservekey(this);
     int64 nValueIn2 = 0;
     std::vector<CTxIn> vCoinsCollateral;