diff --git a/src/policy/policy.h b/src/policy/policy.h
--- a/src/policy/policy.h
+++ b/src/policy/policy.h
@@ -62,7 +62,8 @@
 /**
  * Default for -bytespersigop .
  */
-static const unsigned int DEFAULT_BYTES_PER_SIGOP = 20;
+static const unsigned int DEFAULT_BYTES_PER_SIGOP =
+    1000000 / MAX_BLOCK_SIGOPS_PER_MB;
 /**
  * Min feerate for defining dust. Historically this has been the same as the
  * minRelayTxFee, however changing the dust limit changes which transactions are
@@ -122,7 +123,10 @@
 extern CFeeRate dustRelayFee;
 extern uint32_t nBytesPerSigOp;
 
-/** Compute the virtual transaction size (weight reinterpreted as bytes). */
+/**
+ * Compute the virtual transaction size (size, or more if sigops are too
+ * dense).
+ */
 int64_t GetVirtualTransactionSize(int64_t nSize, int64_t nSigOpCount,
                                   unsigned int bytes_per_sigop);
 int64_t GetVirtualTransactionSize(const CTransaction &tx, int64_t nSigOpCount,
@@ -130,4 +134,9 @@
 int64_t GetVirtualTransactionInputSize(const CTxIn &txin, int64_t nSigOpCount,
                                        unsigned int bytes_per_sigop);
 
+static inline int64_t GetVirtualTransactionSize(int64_t nSize,
+                                                int64_t nSigOpCount) {
+    return GetVirtualTransactionSize(nSize, nSigOpCount, ::nBytesPerSigOp);
+}
+
 #endif // BITCOIN_POLICY_POLICY_H
diff --git a/src/policy/policy.cpp b/src/policy/policy.cpp
--- a/src/policy/policy.cpp
+++ b/src/policy/policy.cpp
@@ -182,7 +182,7 @@
 
 int64_t GetVirtualTransactionSize(int64_t nSize, int64_t nSigOpCount,
                                   unsigned int bytes_per_sigop) {
-    return nSize;
+    return std::max(nSize, nSigOpCount * bytes_per_sigop);
 }
 
 int64_t GetVirtualTransactionSize(const CTransaction &tx, int64_t nSigOpCount,