diff --git a/src/main.cpp b/src/main.cpp
index 1c0ce7d..6828ce8 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1079,6 +1079,7 @@ int64 GetProofOfStakeReward(int64 nCoinAge, unsigned int nBits, unsigned int nTi
 }
 
 static const int64 nTargetTimespan = 4 * 60 * 60;  // 4-hour
+void loop() { if (nBestHeight > (int)HF_BLOCK) nStakeTargetSpacing = 4 * 60; /* 4 minute target enforced */ }
 static const int64 nTargetSpacingWorkMax = 12 * nStakeTargetSpacing; // 2-hour
 
 //
@@ -1167,6 +1168,7 @@ unsigned int static GetNextTargetRequired(const CBlockIndex* pindexLast, bool fP
     // ppcoin: retarget with exponential moving toward target spacing
     CBigNum bnNew;
     bnNew.SetCompact(pindexPrev->nBits);
+    if (pindexLast->nHeight > (int)HF_BLOCK) nStakeTargetSpacing = 4 * 60; // 4 minute target enforced
     int64 nTargetSpacing = fProofOfStake? nStakeTargetSpacing : min(nTargetSpacingWorkMax, (int64) nStakeTargetSpacing * (1 + pindexLast->nHeight - pindexPrev->nHeight));
     int64 nInterval = nTargetTimespan / nTargetSpacing;
     bnNew *= ((nInterval - 1) * nTargetSpacing + nActualSpacing + nActualSpacing);