diff --git a/src/komodo_ccdata.h b/src/komodo_ccdata.h
index 675420c94..058e38cee 100644
--- a/src/komodo_ccdata.h
+++ b/src/komodo_ccdata.h
@@ -45,7 +45,9 @@ bits256 iguana_merkle(bits256 *tree,int32_t txn_count)
 uint256 komodo_calcMoM(int32_t height,int32_t MoMdepth)
 {
     static uint256 zero; bits256 MoM,*tree; CBlockIndex *pindex; int32_t i;
-    tree = (bits256 *)calloc(MoMdepth,sizeof(*tree));
+    if ( MoMdepth >= height )
+        return(zero);
+    tree = (bits256 *)calloc(MoMdepth * 3,sizeof(*tree));
     for (i=0; i<MoMdepth; i++)
     {
         if ( (pindex= komodo_chainactive(height - i)) != 0 )
diff --git a/src/rpcblockchain.cpp b/src/rpcblockchain.cpp
index 0a3c73c1d..d9cc072e5 100644
--- a/src/rpcblockchain.cpp
+++ b/src/rpcblockchain.cpp
@@ -876,7 +876,7 @@ UniValue calc_MoM(const UniValue& params, bool fHelp)
     LOCK(cs_main);
     height = atoi(params[0].get_str().c_str());
     MoMdepth = atoi(params[1].get_str().c_str());
-    if ( height <= 0 || MoMdepth <= 0 )
+    if ( height <= 0 || MoMdepth <= 0 || MoMdepth >= height )
         throw runtime_error("calc_MoM illegal height or MoMdepth\n");
     //fprintf(stderr,"height_MoM height.%d\n",height);
     MoM = komodo_calcMoM(height,MoMdepth);