diff --git a/vlib/compiler/fn.v b/vlib/compiler/fn.v
index aecdd6a82a..efc4ff1dc9 100644
--- a/vlib/compiler/fn.v
+++ b/vlib/compiler/fn.v
@@ -1117,9 +1117,18 @@ fn (p mut Parser) fn_call_args(f mut Fn, generic_param_types []string) {
 			if t.cat == .interface_ {
 				// perform((Speaker) { ._object = &dog,
 				// _interface_idx = _Speaker_Dog_index })
-				concrete_type_name := typ.replace('*', '_ptr')
-				p.cgen.set_placeholder(ph, '($arg.typ) { ._object = &')
-				p.gen(', /*OLD*/ ._interface_idx = _${arg.typ}_${concrete_type_name}_index} /* i. arg*/')
+				$if windows {
+					if !f.is_method {
+						concrete_type_name := typ.replace('*', '_ptr')
+						p.cgen.set_placeholder(ph, '($arg.typ) { ._object = &')
+						p.gen(', /*OLD*/ ._interface_idx = _${arg.typ}_${concrete_type_name}_index} /* i. arg*/')
+					}
+				}
+				$else {
+					concrete_type_name := typ.replace('*', '_ptr')
+					p.cgen.set_placeholder(ph, '($arg.typ) { ._object = &')
+					p.gen(', /*OLD*/ ._interface_idx = _${arg.typ}_${concrete_type_name}_index} /* i. arg*/')
+				}
 				p.table.add_gen_type(arg.typ, typ)
 			}
 		}
@@ -1706,4 +1715,3 @@ pub fn (f &Fn) str_for_error() string {
 	}
 	return s + ')'
 }
-