diff --git a/vlib/v/pref/pref.v b/vlib/v/pref/pref.v
index 053b89d5b7be85..95806b3f93a1f1 100644
--- a/vlib/v/pref/pref.v
+++ b/vlib/v/pref/pref.v
@@ -494,6 +494,7 @@ pub fn parse_args_and_show_errors(known_external_commands []string, args []strin
 			}
 			'-autofree' {
 				res.autofree = true
+				res.gc_mode = .no_gc
 				res.build_options << arg
 			}
 			'-trace-calls' {
diff --git a/vlib/v/slow_tests/valgrind/valgrind_test.v b/vlib/v/slow_tests/valgrind/valgrind_test.v
index 6a0369d20e8451..4dfe1040ef90be 100644
--- a/vlib/v/slow_tests/valgrind/valgrind_test.v
+++ b/vlib/v/slow_tests/valgrind/valgrind_test.v
@@ -87,7 +87,8 @@ fn test_all() {
 		base_filename := os.file_name(test).replace('.v', '')
 		exe_filename := '${wrkdir}/${base_filename}'
 		full_path_to_source_file := os.join_path(vroot, test)
-		compile_cmd := '${os.quoted_path(vexe)} -o ${os.quoted_path(exe_filename)} -cg -cflags "-w" -experimental -gc none -autofree ${os.quoted_path(full_path_to_source_file)}'
+		compile_cmd := '${os.quoted_path(vexe)} -o ${os.quoted_path(exe_filename)} -cg -cflags ' +
+			' "-w" -experimental -autofree ${os.quoted_path(full_path_to_source_file)}'
 		vprintln('compile cmd: ${bold(compile_cmd)}')
 		res := os.execute(compile_cmd)
 		if res.exit_code != 0 {