diff --git a/sys/arm64/arm64/support.S b/sys/arm64/arm64/support.S
index 73ef6a4ac581..914a6e3145e9 100644
--- a/sys/arm64/arm64/support.S
+++ b/sys/arm64/arm64/support.S
@@ -59,6 +59,7 @@ ENTRY(casueword32)
 	ldrb	w0, [x0]		/* Try loading the data */
 2:	SET_FAULT_HANDLER(xzr, x5)	/* Reset the fault handler */
 	str	w4, [x2]		/* Store the read data */
+	mov	x0, #0			/* Success */
 	ret				/* Return */
 END(casueword32)
 
@@ -76,6 +77,7 @@ ENTRY(casueword)
 	ldrb	w0, [x0]		/* Try loading the data */
 2:	SET_FAULT_HANDLER(xzr, x5)	/* Reset the fault handler */
 	str	x4, [x2]		/* Store the read data */
+	mov	x0, #0			/* Success */
 	ret				/* Return */
 END(casueword)