diff --git a/src/bignum.h b/src/bignum.h
index 4143f600..a750025f 100644
--- a/src/bignum.h
+++ b/src/bignum.h
@@ -243,7 +243,7 @@ public:
     std::vector<unsigned char> getvch() const
     {
         unsigned int nSize = BN_bn2mpi(this, NULL);
-        if (nSize < 4)
+        if (nSize <= 4)
             return std::vector<unsigned char>();
         std::vector<unsigned char> vch(nSize);
         BN_bn2mpi(this, &vch[0]);