diff --git a/vlib/v/builder/cc.v b/vlib/v/builder/cc.v
index 5388c832eb..ad83544f8d 100644
--- a/vlib/v/builder/cc.v
+++ b/vlib/v/builder/cc.v
@@ -814,7 +814,7 @@ fn (mut v Builder) build_thirdparty_obj_file(path string, moduleflags []cflag.CF
 		return
 	}
 	println('$obj_path not found, building it in $opath ...')
-	cfile := '${path[..path.len - 2]}.c'
+	cfile := '${obj_path[..obj_path.len - 2]}.c'
 	btarget := moduleflags.c_options_before_target()
 	atarget := moduleflags.c_options_after_target()
 	cppoptions := if v.pref.ccompiler.contains('++') { ' -fpermissive -w ' } else { '' }