diff --git a/src/SerializedTransaction.h b/src/SerializedTransaction.h
index 59f1650ca1..ee4ffb3ea4 100644
--- a/src/SerializedTransaction.h
+++ b/src/SerializedTransaction.h
@@ -28,7 +28,7 @@ protected:
 	TransactionType mType;
 	STVariableLength mSignature;
 	STObject mMiddleTxn, mInnerTxn;
-	TransactionFormat* mFormat;
+	const TransactionFormat* mFormat;
 
 	SerializedTransaction* duplicate() const { return new SerializedTransaction(*this); }
 
diff --git a/src/bignum.h b/src/bignum.h
index 78bce87609..a9a08eda2d 100644
--- a/src/bignum.h
+++ b/src/bignum.h
@@ -27,7 +27,7 @@ private:
 
 protected:
 	BN_CTX* pctx;
-	BN_CTX* operator=(BN_CTX* pnew) { return pctx = pnew; }
+	CAutoBN_CTX& operator=(BN_CTX* pnew) { pctx = pnew; return *this; }
 
 public:
 	CAutoBN_CTX()