--- a/libc/sysdeps/linux/avr32/bits/atomic.h
+++ b/libc/sysdeps/linux/avr32/bits/atomic.h
@@ -28,6 +28,7 @@ typedef uintmax_t uatomic_max_t;
#define __arch_compare_and_exchange_val_32_acq(mem, newval, oldval) \
({ \
+ __uint32_t __result; \
__typeof__(*(mem)) __prev; \
__asm__ __volatile__( \
"/* __arch_compare_and_exchange_val_32_acq */\n" \
