diff --git a/arm/ecc-521-modp.asm b/arm/ecc-521-modp.asm
index c311a891f967f39db1cd96216651caed12e43eb8..3fba23963d2c715583bfbabf185219df342239e1 100644
--- a/arm/ecc-521-modp.asm
+++ b/arm/ecc-521-modp.asm
@@ -91,7 +91,7 @@ PROLOGUE(nettle_ecc_521_modp)
 	adcs	F0, F0, F3, lsr #9
 	C Copy low 9 bits to H, then shift right including carry
 	and	H, F0, T0
-	rrx	F0, F0
+	mov	F0, F0, rrx
 	lsr	F0, F0, #8
 	C Add in F1 = rp[33], with weight 2^1056 = 2^14
 	adds	F0, F0, F1, lsl #14