diff --git a/lib/cm3/sync.c b/lib/cm3/sync.c
index 9257d397..88fe1114 100644
--- a/lib/cm3/sync.c
+++ b/lib/cm3/sync.c
@@ -19,6 +19,10 @@
 
 #include <libopencm3/cm3/sync.h>
 
+#if defined(LPC43XX_M0)
+#warning "Currently sync is not supported on Cortex-M0"
+#else
+
 uint32_t __ldrex(volatile uint32_t *addr)
 {
 	uint32_t res;
@@ -66,3 +70,4 @@ void mutex_unlock(mutex_t *m)
 	*m = MUTEX_UNLOCKED;
 }
 
+#endif