diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index 7223679033..76fd938ce3 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -3474,6 +3474,17 @@ reindex_index(Oid indexId, bool skip_constraint_checks, char persistence,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				 errmsg("cannot reindex temporary tables of other sessions")));
 
+	/*
+	 * Don't allow reindex of an invalid index on TOAST table.  This is a
+	 * leftover from a failed REINDEX CONCURRENTLY, and if rebuilt it would
+	 * not be possible to drop it anymore.
+	 */
+	if (IsToastNamespace(RelationGetNamespace(iRel)) &&
+		!get_index_isvalid(indexId))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("cannot reindex invalid index on TOAST table")));
+
 	/*
 	 * Also check for active uses of the index in the current transaction; we
 	 * don't want to reindex underneath an open indexscan.
@@ -3723,6 +3734,23 @@ reindex_relation(Oid relid, int flags, int options)
 		foreach(indexId, indexIds)
 		{
 			Oid			indexOid = lfirst_oid(indexId);
+			Oid			indexNamespaceId = get_rel_namespace(indexOid);
+
+			/*
+			 * Skip any invalid indexes on a TOAST table.  These can only be
+			 * duplicate leftovers from a failed REINDEX CONCURRENTLY, and if
+			 * rebuilt it would not be possible to drop them anymore.
+			 */
+			if (IsToastNamespace(indexNamespaceId) &&
+				!get_index_isvalid(indexOid))
+			{
+				ereport(WARNING,
+						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+						 errmsg("cannot reindex invalid index \"%s.%s\" on TOAST table, skipping",
+								get_namespace_name(indexNamespaceId),
+								get_rel_name(indexOid))));
+				continue;
+			}
 
 			reindex_index(indexOid, !(flags & REINDEX_REL_CHECK_CONSTRAINTS),
 						  persistence, options);
diff --git a/src/backend/commands/indexcmds.c b/src/backend/commands/indexcmds.c
index 3f3a89fe92..6d696dd672 100644
--- a/src/backend/commands/indexcmds.c
+++ b/src/backend/commands/indexcmds.c
@@ -2868,6 +2868,16 @@ ReindexRelationConcurrently(Oid relationOid, int options)
 							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 							 errmsg("cannot reindex system catalogs concurrently")));
 
+				/*
+				 * Don't allow reindex for an invalid index on TOAST table, as
+				 * if rebuild it would not be possible to drop it.
+				 */
+				if (IsToastNamespace(get_rel_namespace(relationOid)) &&
+					!get_index_isvalid(relationOid))
+					ereport(ERROR,
+							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+							 errmsg("cannot reindex invalid index on TOAST table concurrently")));
+
 				/* Save the list of relation OIDs in private context */
 				oldcontext = MemoryContextSwitchTo(private_context);
 
diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index 3da90cb72a..400e7689fe 100644
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -3227,3 +3227,26 @@ get_index_column_opclass(Oid index_oid, int attno)
 
 	return opclass;
 }
+
+/*
+ * get_index_isvalid
+ *
+ *		Given the index OID, return pg_index.indisvalid.
+ */
+bool
+get_index_isvalid(Oid index_oid)
+{
+	bool		isvalid;
+	HeapTuple	tuple;
+	Form_pg_index rd_index;
+
+	tuple = SearchSysCache1(INDEXRELID, ObjectIdGetDatum(index_oid));
+	if (!HeapTupleIsValid(tuple))
+		elog(ERROR, "cache lookup failed for index %u", index_oid);
+
+	rd_index = (Form_pg_index) GETSTRUCT(tuple);
+	isvalid = rd_index->indisvalid;
+	ReleaseSysCache(tuple);
+
+	return isvalid;
+}
diff --git a/src/include/utils/lsyscache.h b/src/include/utils/lsyscache.h
index f132d39458..131d10eab0 100644
--- a/src/include/utils/lsyscache.h
+++ b/src/include/utils/lsyscache.h
@@ -181,6 +181,7 @@ extern char *get_namespace_name_or_temp(Oid nspid);
 extern Oid	get_range_subtype(Oid rangeOid);
 extern Oid	get_range_collation(Oid rangeOid);
 extern Oid	get_index_column_opclass(Oid index_oid, int attno);
+extern bool get_index_isvalid(Oid index_oid);
 
 #define type_is_array(typid)  (get_element_type(typid) != InvalidOid)
 /* type_is_array_domain accepts both plain arrays and domains over arrays */