diff --git a/src/protocol.cpp b/src/protocol.cpp
index de57f025d34733..a73621f7e42328 100644
--- a/src/protocol.cpp
+++ b/src/protocol.cpp
@@ -265,7 +265,7 @@ 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 af184c9d534dcf..02fdbdb814547f 100644
--- a/src/protocol.h
+++ b/src/protocol.h
@@ -534,7 +534,7 @@ 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); }
 
@@ -555,7 +555,7 @@ class CInv
     const char* GetCommandInternal() const;
 
 public:
-    int type;
+    uint32_t type;
     uint256 hash;
 };
 
diff --git a/test/functional/test_framework/messages.py b/test/functional/test_framework/messages.py
index b289ba2d08573c..5a81ff726cdace 100755
--- a/test/functional/test_framework/messages.py
+++ b/test/functional/test_framework/messages.py
@@ -323,7 +323,7 @@ class CInv:
         MSG_TX: "TX",
         MSG_BLOCK: "Block",
         MSG_FILTERED_BLOCK: "filtered Block",
-        20: "CompactBlock"
+        MSG_CMPCT_BLOCK: "CompactBlock",
     }
 
     def __init__(self, t=0, h=0):
@@ -331,12 +331,12 @@ def __init__(self, t=0, h=0):
         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