diff --git a/include/sys/vdev_impl.h b/include/sys/vdev_impl.h
index 9d4a8062b2d9..c43195ab445f 100644
--- a/include/sys/vdev_impl.h
+++ b/include/sys/vdev_impl.h
@@ -438,6 +438,7 @@ struct vdev {
 	boolean_t	vdev_copy_uberblocks;  /* post expand copy uberblocks */
 	boolean_t	vdev_resilver_deferred;  /* resilver deferred */
 	boolean_t	vdev_kobj_flag; /* kobj event record */
+	boolean_t	vdev_attaching; /* vdev attach ashift handling */
 	vdev_queue_t	vdev_queue;	/* I/O deadline schedule queue	*/
 	vdev_cache_t	vdev_cache;	/* physical block cache		*/
 	spa_aux_vdev_t	*vdev_aux;	/* for l2cache and spares vdevs	*/
diff --git a/module/zfs/vdev.c b/module/zfs/vdev.c
index 57259b8ce88e..247cc373aaeb 100644
--- a/module/zfs/vdev.c
+++ b/module/zfs/vdev.c
@@ -854,9 +854,15 @@ vdev_alloc(spa_t *spa, vdev_t **vdp, nvlist_t *nv, vdev_t *parent, uint_t id,
 	    &vd->vdev_not_present);
 
 	/*
-	 * Get the alignment requirement.
+	 * Get the alignment requirement. Ignore pool ashift for vdev
+	 * attach case.
 	 */
-	(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_ASHIFT, &vd->vdev_ashift);
+	if (alloctype != VDEV_ALLOC_ATTACH) {
+		(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_ASHIFT,
+		    &vd->vdev_ashift);
+	} else {
+		vd->vdev_attaching = B_TRUE;
+	}
 
 	/*
 	 * Retrieve the vdev creation time.
@@ -2093,9 +2099,9 @@ vdev_open(vdev_t *vd)
 				return (SET_ERROR(EDOM));
 			}
 
-			if (vd->vdev_top == vd) {
+			if (vd->vdev_top == vd && vd->vdev_attaching == B_FALSE)
 				vdev_ashift_optimize(vd);
-			}
+			vd->vdev_attaching = B_FALSE;
 		}
 		if (vd->vdev_ashift != 0 && (vd->vdev_ashift < ASHIFT_MIN ||
 		    vd->vdev_ashift > ASHIFT_MAX)) {
diff --git a/tests/zfs-tests/tests/functional/cli_root/zpool_attach/attach-o_ashift.ksh b/tests/zfs-tests/tests/functional/cli_root/zpool_attach/attach-o_ashift.ksh
index 618c6992edb4..7aaf262d4171 100755
--- a/tests/zfs-tests/tests/functional/cli_root/zpool_attach/attach-o_ashift.ksh
+++ b/tests/zfs-tests/tests/functional/cli_root/zpool_attach/attach-o_ashift.ksh
@@ -66,35 +66,14 @@ log_must set_tunable64 VDEV_FILE_PHYSICAL_ASHIFT 16
 typeset ashifts=("9" "10" "11" "12" "13" "14" "15" "16")
 for ashift in ${ashifts[@]}
 do
-	for cmdval in ${ashifts[@]}
-	do
-		log_must zpool create -o ashift=$ashift $TESTPOOL1 $disk1
-		verify_ashift $disk1 $ashift
-		if [[ $? -ne 0 ]]
-		then
-			log_fail "Pool was created without setting ashift " \
-			    "value to $ashift"
-		fi
-		# ashift_of(attached_disk) <= ashift_of(existing_vdev)
-		if [[ $cmdval -le $ashift ]]
-		then
-			log_must zpool attach -o ashift=$cmdval $TESTPOOL1 \
-			    $disk1 $disk2
-			verify_ashift $disk2 $ashift
-			if [[ $? -ne 0 ]]
-			then
-				log_fail "Device was attached without " \
-				    "setting ashift value to $ashift"
-			fi
-		else
-			log_mustnot zpool attach -o ashift=$cmdval $TESTPOOL1 \
-			    $disk1 $disk2
-		fi
-		# clean things for the next run
-		log_must zpool destroy $TESTPOOL1
-		log_must zpool labelclear $disk1
-		log_must zpool labelclear $disk2
-	done
+	log_must zpool create -o ashift=$ashift $TESTPOOL1 $disk1
+	log_must verify_ashift $disk1 $ashift
+	log_must zpool attach $TESTPOOL1 $disk1 $disk2
+	log_must verify_ashift $disk2 $ashift
+	# clean things for the next run
+	log_must zpool destroy $TESTPOOL1
+	log_must zpool labelclear $disk1
+	log_must zpool labelclear $disk2
 done
 
 typeset badvals=("off" "on" "1" "8" "17" "1b" "ff" "-")
diff --git a/tests/zfs-tests/tests/functional/cli_root/zpool_replace/replace-o_ashift.ksh b/tests/zfs-tests/tests/functional/cli_root/zpool_replace/replace-o_ashift.ksh
index 1b18b1297a78..4e79edf43ece 100755
--- a/tests/zfs-tests/tests/functional/cli_root/zpool_replace/replace-o_ashift.ksh
+++ b/tests/zfs-tests/tests/functional/cli_root/zpool_replace/replace-o_ashift.ksh
@@ -66,36 +66,16 @@ log_must set_tunable64 VDEV_FILE_PHYSICAL_ASHIFT 16
 typeset ashifts=("9" "10" "11" "12" "13" "14" "15" "16")
 for ashift in ${ashifts[@]}
 do
-	for cmdval in ${ashifts[@]}
-	do
-		log_must zpool create -o ashift=$ashift $TESTPOOL1 $disk1
-		verify_ashift $disk1 $ashift
-		if [[ $? -ne 0 ]]
-		then
-			log_fail "Pool was created without setting ashift " \
-			    "value to $ashift"
-		fi
-		# ashift_of(replacing_disk) <= ashift_of(existing_vdev)
-		if [[ $cmdval -le $ashift ]]
-		then
-			log_must zpool replace -o ashift=$cmdval $TESTPOOL1 \
-			    $disk1 $disk2
-			verify_ashift $disk2 $ashift
-			if [[ $? -ne 0 ]]
-			then
-				log_fail "Device was replaced without " \
-				    "setting ashift value to $ashift"
-			fi
-			wait_replacing $TESTPOOL1
-		else
-			log_mustnot zpool replace -o ashift=$cmdval $TESTPOOL1 \
-			    $disk1 $disk2
-		fi
-		# clean things for the next run
-		log_must zpool destroy $TESTPOOL1
-		log_must zpool labelclear $disk1
-		log_must zpool labelclear $disk2
-	done
+	log_must zpool create -o ashift=$ashift $TESTPOOL1 $disk1
+	log_must verify_ashift $disk1 $ashift
+	# ashift_of(replacing_disk) <= ashift_of(existing_vdev)
+	log_must zpool replace $TESTPOOL1 $disk1 $disk2
+	log_must verify_ashift $disk2 $ashift
+	wait_replacing $TESTPOOL1
+	# clean things for the next run
+	log_must zpool destroy $TESTPOOL1
+	log_must zpool labelclear $disk1
+	log_must zpool labelclear $disk2
 done
 
 typeset badvals=("off" "on" "1" "8" "17" "1b" "ff" "-")
diff --git a/tests/zfs-tests/tests/functional/cli_root/zpool_replace/replace_prop_ashift.ksh b/tests/zfs-tests/tests/functional/cli_root/zpool_replace/replace_prop_ashift.ksh
index f076f26818eb..9325f93bae87 100755
--- a/tests/zfs-tests/tests/functional/cli_root/zpool_replace/replace_prop_ashift.ksh
+++ b/tests/zfs-tests/tests/functional/cli_root/zpool_replace/replace_prop_ashift.ksh
@@ -72,31 +72,9 @@ do
 	do
 		log_must zpool create -o ashift=$ashift $TESTPOOL1 $disk1
 		log_must zpool set ashift=$pprop $TESTPOOL1
-		# ashift_of(replacing_disk) <= ashift_of(existing_vdev)
-		if [[ $pprop -le $ashift ]]
-		then
-			log_must zpool replace $TESTPOOL1 $disk1 $disk2
-			wait_replacing $TESTPOOL1
-			verify_ashift $disk2 $ashift
-			if [[ $? -ne 0 ]]
-			then
-				log_fail "Device was replaced without " \
-				    "setting ashift value to $ashift"
-			fi
-		else
-			# cannot replace if pool prop ashift > vdev ashift
-			log_mustnot zpool replace $TESTPOOL1 $disk1 $disk2
-			# verify we can override the pool prop value manually
-			log_must zpool replace -o ashift=$ashift $TESTPOOL1 \
-			    $disk1 $disk2
-			wait_replacing $TESTPOOL1
-			verify_ashift $disk2 $ashift
-			if [[ $? -ne 0 ]]
-			then
-				log_fail "Device was replaced without " \
-				    "setting ashift value to $ashift"
-			fi
-		fi
+		log_must zpool replace $TESTPOOL1 $disk1 $disk2
+		wait_replacing $TESTPOOL1
+		log_must verify_ashift $disk2 $ashift
 		# clean things for the next run
 		log_must zpool destroy $TESTPOOL1
 		log_must zpool labelclear $disk1