diff --git a/src/rpcmining.cpp b/src/rpcmining.cpp
index 67a0fb07b..01f205ce3 100644
--- a/src/rpcmining.cpp
+++ b/src/rpcmining.cpp
@@ -21,6 +21,8 @@
 using namespace json_spirit;
 using namespace std;
 
+static const int kLookupSpanMod = 240;
+
 #ifdef ENABLE_WALLET
 // Key used by getwork miners.
 // Allocated in InitRPCMining, free'd in ShutdownRPCMining
@@ -65,7 +67,7 @@ Value GetNetworkHashPS(int lookup, int height) {
 
     // If lookup is -1, then use blocks since last difficulty change.
     if (lookup <= 0)
-        lookup = pb->nHeight % 2016 + 1;
+        lookup = pb->nHeight % kLookupSpanMod + 1;
 
     // If lookup is larger than chain, then set it to chain length.
     if (lookup > pb->nHeight)