diff --git a/db/osqlcomm.c b/db/osqlcomm.c
index 44d93ef011..e2cdb8a7b6 100644
--- a/db/osqlcomm.c
+++ b/db/osqlcomm.c
@@ -5977,14 +5977,16 @@ static int _process_partitioned_table_merge(struct ireq *iq)
         sc->kind = SC_ADDTABLE;
 
         rc = start_schema_change_tran(iq, NULL);
-        iq->sc->sc_next = iq->sc_pending;
-        iq->sc_pending = iq->sc;
+
         if (rc != SC_COMMIT_PENDING) {
             if (rc != SC_MASTER_DOWNGRADE)
                 iq->osql_flags |= OSQL_FLAGS_SCDONE;
             return ERR_SC;
         }
+
         arg.indx = -1; /* see timepart_foreach_shardname NOTE */
+        iq->sc->sc_next = iq->sc_pending;
+        iq->sc_pending = iq->sc;
     } else {
         /*
          * use the fast shard as the destination, after first altering it
@@ -5995,13 +5997,15 @@ static int _process_partitioned_table_merge(struct ireq *iq)
         strncpy(sc->tablename, first_shard->tablename, sizeof(sc->tablename));
 
         rc = start_schema_change_tran(iq, NULL);
-        iq->sc->sc_next = iq->sc_pending;
-        iq->sc_pending = iq->sc;
         if (rc != SC_COMMIT_PENDING) {
             if (rc != SC_MASTER_DOWNGRADE)
                 iq->osql_flags |= OSQL_FLAGS_SCDONE;
             return ERR_SC;
         }
+
+        iq->sc->sc_next = iq->sc_pending;
+        iq->sc_pending = iq->sc;
+
         arg.check_extra_shard = 1;
         strncpy(sc->newtable, sc->tablename, sizeof(sc->newtable)); /* piggyback a rename with alter */
         arg.indx = 0;                                               /* see timepart_foreach_shardname NOTE */
diff --git a/tests/timepart_trunc.test/runit b/tests/timepart_trunc.test/runit
index bf1ec94b13..18c212cba3 100755
--- a/tests/timepart_trunc.test/runit
+++ b/tests/timepart_trunc.test/runit
@@ -419,13 +419,26 @@ $cmd "select * from t14 order by 1" >> $OUT
 
 timepart_stats 0
 
-echo $cmd "ALTER TABLE t14 PARTITIONED BY NONE"
-$cmd "ALTER TABLE t14 PARTITIONED BY NONE"
-if (( $? != 0 )) ; then
-   echo "FAILURE to remote partitioning for t14"
+$cmdm "exec procedure sys.cmd.send('convert_record_sleep 1')"
+
+echo $cmd "ALTER TABLE t14 PARTITIONED BY NONE &"
+$cmd "ALTER TABLE t14 PARTITIONED BY NONE" &
+waitpid=$!
+
+sleep 1
+
+if $cmd "ALTER TABLE t14 PARTITIONED BY NONE"; then
+   echo "FAILURE to block concurrent schema change"
    exit 1
 fi
 
+if ! wait $waitpid; then
+   echo "FAILURE to remove partitioning for t14"
+   exit 1
+fi
+
+$cmdm "exec procedure sys.cmd.send('convert_record_sleep 0')"
+
 echo $cmd "select * from t14 order by 1"
 echo $cmd "select * from t14 order by 1" >> $OUT
 $cmd "select * from t14 order by 1" >> $OUT