diff --git a/vlib/v/gen/c/auto_eq_methods.v b/vlib/v/gen/c/auto_eq_methods.v
index 4009e86ee7..bcd87cac85 100644
--- a/vlib/v/gen/c/auto_eq_methods.v
+++ b/vlib/v/gen/c/auto_eq_methods.v
@@ -628,7 +628,7 @@ fn (mut g Gen) gen_interface_equality_fn(left_type ast.Type) string {
 
 	fn_builder.writeln('${g.static_non_parallel}inline bool ${fn_name}_interface_eq(${ptr_styp} a, ${ptr_styp} b) {')
 	fn_builder.writeln('\tif (${left_arg} == ${right_arg}) {')
-	fn_builder.writeln('\t\tint idx = v_typeof_interface_idx_${idx_fn}(${left_arg});')
+	fn_builder.writeln('\t\tu32 idx = v_typeof_interface_idx_${idx_fn}(${left_arg});')
 	if info is ast.Interface {
 		for typ in info.types {
 			sym := g.table.sym(typ.set_nr_muls(0))
diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index b615c06ca5..fdb4625221 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -1918,7 +1918,7 @@ pub fn (mut g Gen) write_interface_typesymbol_declaration(sym ast.TypeSymbol) {
 		g.type_definitions.writeln('\t\t${vcname}* _${vcname};')
 	}
 	g.type_definitions.writeln('\t};')
-	g.type_definitions.writeln('\tint _typ;')
+	g.type_definitions.writeln('\tu32 _typ;')
 	for field in info.fields {
 		styp := g.styp(field.typ)
 		cname := c_name(field.name)
@@ -6975,7 +6975,7 @@ fn (mut g Gen) write_types(symbols []&ast.TypeSymbol) {
 					g.type_definitions.writeln('\t\t${var_type} _${variant_name};')
 				}
 				g.type_definitions.writeln('\t};')
-				g.type_definitions.writeln('\tint _typ;')
+				g.type_definitions.writeln('\tu32 _typ;')
 				if sym.info.fields.len > 0 {
 					g.writeln('\t// pointers to common sumtype fields')
 					for field in sym.info.fields {