diff --git a/builder/builtins.go b/builder/builtins.go
index 8bd243e7..9a1eb148 100644
--- a/builder/builtins.go
+++ b/builder/builtins.go
@@ -158,7 +158,7 @@ var aeabiBuiltins = []string{
 
 func builtinFiles(target string) []string {
 	builtins := append([]string{}, genericBuiltins...) // copy genericBuiltins
-	if strings.HasPrefix(target, "arm") {
+	if strings.HasPrefix(target, "arm") || strings.HasPrefix(target, "thumb") {
 		builtins = append(builtins, aeabiBuiltins...)
 	}
 	return builtins
diff --git a/targets/gameboy-advance.json b/targets/gameboy-advance.json
index bc751d0c..efad489c 100644
--- a/targets/gameboy-advance.json
+++ b/targets/gameboy-advance.json
@@ -6,6 +6,7 @@
 	"goarch": "arm",
 	"compiler": "clang",
 	"linker": "ld.lld",
+	"rtlib": "compiler-rt",
 	"cflags": [
 		"-g",
 		"--target=thumb4-none-eabi",