diff --git a/module/zfs/spa_misc.c b/module/zfs/spa_misc.c
index 1640dcedd..540fd1077 100644
--- a/module/zfs/spa_misc.c
+++ b/module/zfs/spa_misc.c
@@ -1807,10 +1807,11 @@ spa_update_dspace(spa_t *spa)
 	    ddt_get_dedup_dspace(spa);
 	if (spa->spa_vdev_removal != NULL) {
 		/*
-		 * We can't allocate from the removing device, so
-		 * subtract its size.  This prevents the DMU/DSL from
-		 * filling up the (now smaller) pool while we are in the
-		 * middle of removing the device.
+		 * We can't allocate from the removing device, so subtract
+		 * its size if it was included in dspace (i.e. if this is a
+		 * normal-class vdev, not special/dedup).  This prevents the
+		 * DMU/DSL from filling up the (now smaller) pool while we
+		 * are in the middle of removing the device.
 		 *
 		 * Note that the DMU/DSL doesn't actually know or care
 		 * how much space is allocated (it does its own tracking
@@ -1822,8 +1823,10 @@ spa_update_dspace(spa_t *spa)
 		spa_config_enter(spa, SCL_VDEV, FTAG, RW_READER);
 		vdev_t *vd =
 		    vdev_lookup_top(spa, spa->spa_vdev_removal->svr_vdev_id);
-		spa->spa_dspace -= spa_deflate(spa) ?
-		    vd->vdev_stat.vs_dspace : vd->vdev_stat.vs_space;
+		if (vd->vdev_mg->mg_class == spa_normal_class(spa)) {
+			spa->spa_dspace -= spa_deflate(spa) ?
+			    vd->vdev_stat.vs_dspace : vd->vdev_stat.vs_space;
+		}
 		spa_config_exit(spa, SCL_VDEV, FTAG);
 	}
 }
diff --git a/module/zfs/vdev_removal.c b/module/zfs/vdev_removal.c
index ed7d1d4b3..3bccb9d7d 100644
--- a/module/zfs/vdev_removal.c
+++ b/module/zfs/vdev_removal.c
@@ -993,7 +993,7 @@ spa_vdev_copy_segment(vdev_t *vd, range_tree_t *segs,
 	 * An allocation class might not have any remaining vdevs or space
 	 */
 	metaslab_class_t *mc = mg->mg_class;
-	if (mc != spa_normal_class(spa) && mc->mc_groups <= 1)
+	if (mc->mc_groups == 0)
 		mc = spa_normal_class(spa);
 	int error = metaslab_alloc_dva(spa, mc, size, &dst, 0, NULL, txg, 0,
 	    zal, 0);
@@ -1976,32 +1976,38 @@ spa_vdev_remove_top_check(vdev_t *vd)
 	if (!spa_feature_is_enabled(spa, SPA_FEATURE_DEVICE_REMOVAL))
 		return (SET_ERROR(ENOTSUP));
 
-	/* available space in the pool's normal class */
-	uint64_t available = dsl_dir_space_available(
-	    spa->spa_dsl_pool->dp_root_dir, NULL, 0, B_TRUE);
 
 	metaslab_class_t *mc = vd->vdev_mg->mg_class;
-
-	/*
-	 * When removing a vdev from an allocation class that has
-	 * remaining vdevs, include available space from the class.
-	 */
-	if (mc != spa_normal_class(spa) && mc->mc_groups > 1) {
-		uint64_t class_avail = metaslab_class_get_space(mc) -
-		    metaslab_class_get_alloc(mc);
-
-		/* add class space, adjusted for overhead */
-		available += (class_avail * 94) / 100;
-	}
-
-	/*
-	 * There has to be enough free space to remove the
-	 * device and leave double the "slop" space (i.e. we
-	 * must leave at least 3% of the pool free, in addition to
-	 * the normal slop space).
-	 */
-	if (available < vd->vdev_stat.vs_dspace + spa_get_slop_space(spa)) {
-		return (SET_ERROR(ENOSPC));
+	metaslab_class_t *normal = spa_normal_class(spa);
+	if (mc != normal) {
+		/*
+		 * Space allocated from the special (or dedup) class is
+		 * included in the DMU's space usage, but it's not included
+		 * in spa_dspace (or dsl_pool_adjustedsize()).  Therefore
+		 * there is always at least as much free space in the normal
+		 * class, as is allocated from the special (and dedup) class.
+		 * As a backup check, we will return ENOSPC if this is
+		 * violated. See also spa_update_dspace().
+		 */
+		uint64_t available = metaslab_class_get_space(normal) -
+		    metaslab_class_get_alloc(normal);
+		ASSERT3U(available, >=, vd->vdev_stat.vs_alloc);
+		if (available < vd->vdev_stat.vs_alloc)
+			return (SET_ERROR(ENOSPC));
+	} else {
+		/* available space in the pool's normal class */
+		uint64_t available = dsl_dir_space_available(
+		    spa->spa_dsl_pool->dp_root_dir, NULL, 0, B_TRUE);
+		if (available <
+		    vd->vdev_stat.vs_dspace + spa_get_slop_space(spa)) {
+			/*
+			 * This is a normal device. There has to be enough free
+			 * space to remove the device and leave double the
+			 * "slop" space (i.e. we must leave at least 3% of the
+			 * pool free, in addition to the normal slop space).
+			 */
+			return (SET_ERROR(ENOSPC));
+		}
 	}
 
 	/*
diff --git a/tests/test-runner/bin/zts-report.py.in b/tests/test-runner/bin/zts-report.py.in
index 6b5cd191c..05b53bb4c 100755
--- a/tests/test-runner/bin/zts-report.py.in
+++ b/tests/test-runner/bin/zts-report.py.in
@@ -187,8 +187,6 @@ elif sys.platform.startswith('linux'):
 # reasons listed above can be used.
 #
 maybe = {
-    'alloc_class/alloc_class_012_pos': ['FAIL', '9142'],
-    'alloc_class/alloc_class_013_pos': ['FAIL', '9142'],
     'chattr/setup': ['SKIP', exec_reason],
     'cli_root/zdb/zdb_006_pos': ['FAIL', known_reason],
     'cli_root/zfs_get/zfs_get_004_pos': ['FAIL', known_reason],
diff --git a/tests/zfs-tests/tests/functional/alloc_class/alloc_class_012_pos.ksh b/tests/zfs-tests/tests/functional/alloc_class/alloc_class_012_pos.ksh
index 1cfe6642d..b49a8919e 100755
--- a/tests/zfs-tests/tests/functional/alloc_class/alloc_class_012_pos.ksh
+++ b/tests/zfs-tests/tests/functional/alloc_class/alloc_class_012_pos.ksh
@@ -33,8 +33,9 @@ function file_in_special_vdev # <dataset> <inode>
 {
 	typeset dataset="$1"
 	typeset inum="$2"
+	typeset num_normal=$(echo $ZPOOL_DISKS | wc -w | xargs)
 
-	zdb -dddddd $dataset $inum | awk '{
+	zdb -dddddd $dataset $inum | awk -v d=$num_normal '{
 # find DVAs from string "offset level dva" only for L0 (data) blocks
 if (match($0,"L0 [0-9]+")) {
    dvas[0]=$3
@@ -49,7 +50,7 @@ if (match($0,"L0 [0-9]+")) {
             exit 1;
          }
          # verify vdev is "special"
-         if (arr[1] < 3) {
+         if (arr[1] < d) {
             exit 1;
          }
       }