diff --git a/sys/arm64/include/armreg.h b/sys/arm64/include/armreg.h
index 953c9af220b9..c43ec1f5b97c 100644
--- a/sys/arm64/include/armreg.h
+++ b/sys/arm64/include/armreg.h
@@ -1981,6 +1981,15 @@
 #define	PMXEVTYPER_EL0_CRm		13
 #define	PMXEVTYPER_EL0_op2		1
 
+/* RNDRRS */
+#define	RNDRRS				MRS_REG(RNDRRS)
+#define	RNDRRS_REG			MRS_REG_ALT_NAME(RNDRRS)
+#define	RNDRRS_op0			3
+#define	RNDRRS_op1			3
+#define	RNDRRS_CRn			2
+#define	RNDRRS_CRm			4
+#define	RNDRRS_op2			1
+
 /* SCTLR_EL1 - System Control Register */
 #define	SCTLR_RES1	0x30d00800	/* Reserved ARMv8.0, write 1 */
 #define	SCTLR_M				(UL(0x1) << 0)
diff --git a/sys/dev/random/armv8rng.c b/sys/dev/random/armv8rng.c
index 3cca42a5bbf3..61698bfff820 100644
--- a/sys/dev/random/armv8rng.c
+++ b/sys/dev/random/armv8rng.c
@@ -59,10 +59,10 @@ random_rndr_read_one(u_long *buf)
 	loop = 10;
 	do {
 		__asm __volatile(
-		    ".arch_extension rng   \n"
-		    "mrs	%0, rndrrs \n" /* Read the random number */
-		    "cset	%w1, ne    \n" /* 1 on success, 0 on failure */
-		    ".arch_extension norng \n"
+		    /* Read the random number */
+		    "mrs	%0, " __XSTRING(RNDRRS_REG) "\n"
+		    /* 1 on success, 0 on failure */
+		    "cset	%w1, ne\n"
 		    : "=&r" (val), "=&r"(ret) :: "cc");
 	} while (ret != 0 && --loop > 0);