diff --git a/src/script/sign.h b/src/script/sign.h
--- a/src/script/sign.h
+++ b/src/script/sign.h
@@ -158,27 +158,25 @@
 // The separator has no value.
 static constexpr uint8_t PSBT_SEPARATOR = 0x00;
 
-// Takes a stream and multiple arguments and serializes them into a vector and
-// then into the stream. The resulting output into the stream has the total
-// serialized length of all of the objects followed by all objects concatenated
-// with each other.
+// Takes a stream and multiple arguments and serializes them as if first
+// serialized into a vector and then into the stream. The resulting output into
+// the stream has the total serialized length of all of the objects followed by
+// all objects concatenated with each other.
 template <typename Stream, typename... X>
 void SerializeToVector(Stream &s, const X &... args) {
-    std::vector<uint8_t> ret;
-    CVectorWriter ss(SER_NETWORK, PROTOCOL_VERSION, ret, 0);
-    SerializeMany(ss, args...);
-    s << ret;
+    WriteCompactSize(s, GetSerializeSizeMany(s, args...));
+    SerializeMany(s, args...);
 }
 
 // Takes a stream and multiple arguments and unserializes them first as a vector
-// then each object individually in the order provided in the arguments
+// then each object individually in the order provided in the arguments.
 template <typename Stream, typename... X>
 void UnserializeFromVector(Stream &s, X &... args) {
-    std::vector<uint8_t> data;
-    s >> data;
-    CDataStream ss(data, SER_NETWORK, PROTOCOL_VERSION);
-    UnserializeMany(ss, args...);
-    if (!ss.eof()) {
+    size_t expected_size = ReadCompactSize(s);
+    size_t remaining_before = s.size();
+    UnserializeMany(s, args...);
+    size_t remaining_after = s.size();
+    if (remaining_after + expected_size != remaining_before) {
         throw std::ios_base::failure("Size of value was not the stated size");
     }
 }
diff --git a/src/serialize.h b/src/serialize.h
--- a/src/serialize.h
+++ b/src/serialize.h
@@ -993,4 +993,11 @@
     return (CSizeComputer(s.GetVersion()) << t).size();
 }
 
+template <typename S, typename... T>
+size_t GetSerializeSizeMany(const S &s, const T &... t) {
+    CSizeComputer sc(s.GetVersion());
+    SerializeMany(sc, t...);
+    return sc.size();
+}
+
 #endif // BITCOIN_SERIALIZE_H