diff --git a/include/sys/spa.h b/include/sys/spa.h
index b6e124faa38d..e2f27ed60b82 100644
--- a/include/sys/spa.h
+++ b/include/sys/spa.h
@@ -802,6 +802,7 @@ extern uint64_t spa_load_guid(spa_t *spa);
 extern uint64_t spa_last_synced_txg(spa_t *spa);
 extern uint64_t spa_first_txg(spa_t *spa);
 extern uint64_t spa_syncing_txg(spa_t *spa);
+extern uint64_t spa_final_dirty_txg(spa_t *spa);
 extern uint64_t spa_version(spa_t *spa);
 extern pool_state_t spa_state(spa_t *spa);
 extern spa_load_state_t spa_load_state(spa_t *spa);
diff --git a/module/zfs/dbuf.c b/module/zfs/dbuf.c
index ce99fd54c155..096d183584c3 100644
--- a/module/zfs/dbuf.c
+++ b/module/zfs/dbuf.c
@@ -1639,6 +1639,7 @@ dbuf_dirty(dmu_buf_impl_t *db, dmu_tx_t *tx)
 	 * this assertion only if we're not already dirty.
 	 */
 	os = dn->dn_objset;
+	VERIFY3U(tx->tx_txg, <=, spa_final_dirty_txg(os->os_spa));
 #ifdef DEBUG
 	if (dn->dn_objset->os_dsl_dataset != NULL)
 		rrw_enter(&os->os_dsl_dataset->ds_bp_rwlock, RW_READER, FTAG);
diff --git a/module/zfs/metaslab.c b/module/zfs/metaslab.c
index 3fd7f9049c8b..5e413c06518b 100644
--- a/module/zfs/metaslab.c
+++ b/module/zfs/metaslab.c
@@ -1582,15 +1582,22 @@ metaslab_set_fragmentation(metaslab_t *msp)
 	 * so that we upgrade next time we encounter it.
 	 */
 	if (msp->ms_sm->sm_dbuf->db_size != sizeof (space_map_phys_t)) {
+		uint64_t txg = spa_syncing_txg(spa);
 		vdev_t *vd = msp->ms_group->mg_vd;
 
-		if (spa_writeable(vd->vdev_spa)) {
-			uint64_t txg = spa_syncing_txg(spa);
-
+		/*
+		 * If we've reached the final dirty txg, then we must
+		 * be shutting down the pool. We don't want to dirty
+		 * any data past this point so skip setting the condense
+		 * flag. We can retry this action the next time the pool
+		 * is imported.
+		 */
+		if (spa_writeable(spa) && txg < spa_final_dirty_txg(spa)) {
 			msp->ms_condense_wanted = B_TRUE;
 			vdev_dirty(vd, VDD_METASLAB, msp, txg + 1);
 			spa_dbgmsg(spa, "txg %llu, requesting force condense: "
-			    "msp %p, vd %p", txg, msp, vd);
+			    "ms_id %llu, vdev_id %llu", txg, msp->ms_id,
+			    vd->vdev_id);
 		}
 		msp->ms_fragmentation = ZFS_FRAG_INVALID;
 		return;
@@ -2217,13 +2224,17 @@ metaslab_sync(metaslab_t *msp, uint64_t txg)
 	/*
 	 * Normally, we don't want to process a metaslab if there
 	 * are no allocations or frees to perform. However, if the metaslab
-	 * is being forced to condense we need to let it through.
+	 * is being forced to condense and it's loaded, we need to let it
+	 * through.
 	 */
 	if (range_tree_space(alloctree) == 0 &&
 	    range_tree_space(msp->ms_freeingtree) == 0 &&
-	    !msp->ms_condense_wanted)
+	    !(msp->ms_loaded && msp->ms_condense_wanted))
 		return;
 
+
+	VERIFY(txg <= spa_final_dirty_txg(spa));
+
 	/*
 	 * The only state that can actually be changing concurrently with
 	 * metaslab_sync() is the metaslab's ms_tree.  No other thread can
diff --git a/module/zfs/spa_misc.c b/module/zfs/spa_misc.c
index ea16e69f0603..39a1d7d6a186 100644
--- a/module/zfs/spa_misc.c
+++ b/module/zfs/spa_misc.c
@@ -1596,6 +1596,16 @@ spa_syncing_txg(spa_t *spa)
 	return (spa->spa_syncing_txg);
 }
 
+/*
+ * Return the last txg where data can be dirtied. The final txgs
+ * will be used to just clear out any deferred frees that remain.
+ */
+uint64_t
+spa_final_dirty_txg(spa_t *spa)
+{
+	return (spa->spa_final_txg - TXG_DEFER_SIZE);
+}
+
 pool_state_t
 spa_state(spa_t *spa)
 {
diff --git a/module/zfs/space_map.c b/module/zfs/space_map.c
index 961f23b0edb5..a8f88b6710fe 100644
--- a/module/zfs/space_map.c
+++ b/module/zfs/space_map.c
@@ -23,7 +23,7 @@
  * Use is subject to license terms.
  */
 /*
- * Copyright (c) 2012, 2014 by Delphix. All rights reserved.
+ * Copyright (c) 2012, 2016 by Delphix. All rights reserved.
  */
 
 #include <sys/zfs_context.h>
@@ -411,6 +411,7 @@ space_map_truncate(space_map_t *sm, dmu_tx_t *tx)
 
 	ASSERT(dsl_pool_sync_context(dmu_objset_pool(os)));
 	ASSERT(dmu_tx_is_syncing(tx));
+	VERIFY3U(dmu_tx_get_txg(tx), <=, spa_final_dirty_txg(spa));
 
 	dmu_object_info_from_db(sm->sm_dbuf, &doi);
 
@@ -425,9 +426,10 @@ space_map_truncate(space_map_t *sm, dmu_tx_t *tx)
 	if ((spa_feature_is_enabled(spa, SPA_FEATURE_SPACEMAP_HISTOGRAM) &&
 	    doi.doi_bonus_size != sizeof (space_map_phys_t)) ||
 	    doi.doi_data_block_size != space_map_blksz) {
-		zfs_dbgmsg("txg %llu, spa %s, reallocating: "
-		    "old bonus %llu, old blocksz %u", dmu_tx_get_txg(tx),
-		    spa_name(spa), doi.doi_bonus_size, doi.doi_data_block_size);
+		zfs_dbgmsg("txg %llu, spa %s, sm %p, reallocating "
+		    "object[%llu]: old bonus %u, old blocksz %u",
+		    dmu_tx_get_txg(tx), spa_name(spa), sm, sm->sm_object,
+		    doi.doi_bonus_size, doi.doi_data_block_size);
 
 		space_map_free(sm, tx);
 		dmu_buf_rele(sm->sm_dbuf, sm);