diff --git a/src/pow.cpp b/src/pow.cpp
index d6cbc2e19..188961e8b 100644
--- a/src/pow.cpp
+++ b/src/pow.cpp
@@ -168,7 +168,7 @@ arith_uint256 oldRT_CST_RST(int32_t height,uint32_t nTime,arith_uint256 bnTarget
 arith_uint256 RT_CST_RST_outer(int32_t height,uint32_t nTime,arith_uint256 bnTarget,uint32_t *ts,arith_uint256 *ct,int32_t numerator,int32_t denominator,int32_t W,int32_t past)
 {
     int64_t outerK; arith_uint256 mintarget = bnTarget / arith_uint256(2);
-    if ( (ts[0] - ts[W]) < (T * numerator)/denominator )
+    if ( (ts[0] - ts[W+1]) < (T * numerator)/denominator )
     {
         outerK = (K * (nTime-ts[0]) * (ts[0]-ts[W]) * denominator) / (numerator * (T * T));
         if ( outerK < K )