diff --git a/src/data.cpp b/src/data.cpp
index f270c23..019e8d5 100644
--- a/src/data.cpp
+++ b/src/data.cpp
@@ -565,7 +565,7 @@ void Value::copyIn(const void *ptr, StoreType type)
     case StoreType::UInteger: {
         if(!copyInScalar(store->as<uint64_t>(), ptr, type)) throw NoConvert(SB()<<"Unable to assign "<<desc->code<<" with "<<type);
         // truncate as if assigned to narrower type
-        int64_t orig = store->as<int64_t>();
+        uint64_t orig = store->as<uint64_t>();
         switch(desc->code.code) {
         case TypeCode::UInt8: orig = uint8_t(orig); break;
         case TypeCode::UInt16: orig = uint16_t(orig); break;
@@ -573,7 +573,7 @@ void Value::copyIn(const void *ptr, StoreType type)
         case TypeCode::UInt64: orig = uint64_t(orig); break;
         default: break;
         }
-        store->as<int64_t>() = orig;
+        store->as<uint64_t>() = orig;
         break;
     }
     case StoreType::Bool: {
diff --git a/src/dataencode.cpp b/src/dataencode.cpp
index 5bf3990..d2d90c6 100644
--- a/src/dataencode.cpp
+++ b/src/dataencode.cpp
@@ -491,10 +491,10 @@ void from_wire_field(Buffer& buf, TypeStore& ctxt,  const FieldDesc* desc, const
     case StoreType::UInteger: {
         auto& fld = store->as<uint64_t>();
         switch(desc->code.code) {
-        case TypeCode::UInt8:  fld = from_wire_as<int8_t>(buf); return;
-        case TypeCode::UInt16: fld = from_wire_as<int16_t>(buf); return;
-        case TypeCode::UInt32: fld = from_wire_as<int32_t>(buf); return;
-        case TypeCode::UInt64: fld = from_wire_as<int64_t>(buf); return;
+        case TypeCode::UInt8:  fld = from_wire_as<uint8_t>(buf); return;
+        case TypeCode::UInt16: fld = from_wire_as<uint16_t>(buf); return;
+        case TypeCode::UInt32: fld = from_wire_as<uint32_t>(buf); return;
+        case TypeCode::UInt64: fld = from_wire_as<uint64_t>(buf); return;
         default: break;
         }
     }