diff --git a/src/arith_uint256.cpp b/src/arith_uint256.cpp
index 2e6136357..be1a44bba 100644
--- a/src/arith_uint256.cpp
+++ b/src/arith_uint256.cpp
@@ -109,6 +109,11 @@ base_uint<BITS>& base_uint<BITS>::operator/=(const base_uint& b)
 template <unsigned int BITS>
 int base_uint<BITS>::CompareTo(const base_uint<BITS>& b) const
 {
+    if ( pn == 0 || b.pn == 0 )
+    {
+        fprintf(stderr,"CompareTo null %p or %p\n",pn,b.pn);
+        return(0);
+    }
     for (int i = WIDTH - 1; i >= 0; i--) {
         if (pn[i] < b.pn[i])
             return -1;