diff --git a/src/pow.cpp b/src/pow.cpp
index bdcfa852f..73579b1cd 100644
--- a/src/pow.cpp
+++ b/src/pow.cpp
@@ -41,9 +41,15 @@ unsigned int GetNextWorkRequired(const CBlockIndex* pindexLast, const CBlockHead
         return pindexLast->nBits;
     }
 
+    // Litecoin: This fixes an issue where a 51% attack can change difficulty at will.
+    // Go back the full period unless it's the first retarget after genesis. Code courtesy of Art Forz
+    int blockstogoback = Params().Interval()-1;
+    if ((pindexLast->nHeight+1) != Params().Interval())
+        blockstogoback = Params().Interval();
+
     // Go back by what we want to be 14 days worth of blocks
     const CBlockIndex* pindexFirst = pindexLast;
-    for (int i = 0; pindexFirst && i < Params().Interval()-1; i++)
+    for (int i = 0; pindexFirst && i < blockstogoback; i++)
         pindexFirst = pindexFirst->pprev;
     assert(pindexFirst);