diff --git a/src/protocol.cpp b/src/protocol.cpp
index c989aa3902c..1f2e628545e 100644
--- a/src/protocol.cpp
+++ b/src/protocol.cpp
@@ -163,7 +163,7 @@ CInv::CInv()
     hash.SetNull();
 }
 
-CInv::CInv(int typeIn, const uint256& hashIn) : type(typeIn), hash(hashIn) {}
+CInv::CInv(uint32_t typeIn, const uint256& hashIn) : type(typeIn), hash(hashIn) {}
 
 bool operator<(const CInv& a, const CInv& b)
 {
diff --git a/src/protocol.h b/src/protocol.h
index a059bf482ad..7fb84cddf11 100644
--- a/src/protocol.h
+++ b/src/protocol.h
@@ -408,7 +408,7 @@ class CInv
 {
 public:
     CInv();
-    CInv(int typeIn, const uint256& hashIn);
+    CInv(uint32_t typeIn, const uint256& hashIn);
 
     SERIALIZE_METHODS(CInv, obj) { READWRITE(obj.type, obj.hash); }
 
@@ -435,7 +435,7 @@ public:
         return type == MSG_BLOCK || type == MSG_FILTERED_BLOCK || type == MSG_CMPCT_BLOCK || type == MSG_WITNESS_BLOCK;
     }
 
-    int type;
+    uint32_t type;
     uint256 hash;
 };
 
diff --git a/test/functional/test_framework/messages.py b/test/functional/test_framework/messages.py
index 8d68af2d070..b4e609df3a3 100755
--- a/test/functional/test_framework/messages.py
+++ b/test/functional/test_framework/messages.py
@@ -245,8 +245,8 @@ class CInv:
         MSG_TX | MSG_WITNESS_FLAG: "WitnessTx",
         MSG_BLOCK | MSG_WITNESS_FLAG: "WitnessBlock",
         MSG_FILTERED_BLOCK: "filtered Block",
-        4: "CompactBlock",
-        5: "WTX",
+        MSG_CMPCT_BLOCK: "CompactBlock",
+        MSG_WTX: "WTX",
     }
 
     def __init__(self, t=0, h=0):
@@ -254,12 +254,12 @@ class CInv:
         self.hash = h
 
     def deserialize(self, f):
-        self.type = struct.unpack("<i", f.read(4))[0]
+        self.type = struct.unpack("<I", f.read(4))[0]
         self.hash = deser_uint256(f)
 
     def serialize(self):
         r = b""
-        r += struct.pack("<i", self.type)
+        r += struct.pack("<I", self.type)
         r += ser_uint256(self.hash)
         return r