diff --git a/src/backend/optimizer/plan/analyzejoins.c b/src/backend/optimizer/plan/analyzejoins.c
index 2da2a6c14e..334ea8d3bb 100644
--- a/src/backend/optimizer/plan/analyzejoins.c
+++ b/src/backend/optimizer/plan/analyzejoins.c
@@ -1751,6 +1751,48 @@ update_eclasses(PlannerInfo *root, EquivalenceClass *ec, int from, int to)
 	bms_free(ec->ec_source_indexes);
 	ec->ec_source_indexes = new_source_indexes;
 	ec->ec_relids = replace_relid(ec->ec_relids, from, to);
+
+#ifdef USE_ASSERT_CHECKING
+	/*
+	 * Sanity check:
+	 * Verify that there are no missing references between RestrictInfos and
+	 * our indexes, namely eclass_source_indexes and eclass_derive_indexes.
+	 */
+
+	foreach(lc, root->eq_sources)
+	{
+		RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
+		int			index;
+		int			k;
+
+		if (rinfo == NULL)
+			continue;
+
+		index = list_cell_number(root->eq_sources, lc);
+		k = -1;
+		while ((k = bms_next_member(rinfo->clause_relids, k)) >= 0)
+		{
+			Assert(bms_is_member(index, root->simple_rte_array[k]->eclass_source_indexes));
+		}
+	}
+
+	foreach(lc, root->eq_derives)
+	{
+		RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
+		int			index;
+		int			k;
+
+		if (rinfo == NULL)
+			continue;
+
+		index = list_cell_number(root->eq_derives, lc);
+		k = -1;
+		while ((k = bms_next_member(rinfo->clause_relids, k)) >= 0)
+		{
+			Assert(bms_is_member(index, root->simple_rte_array[k]->eclass_derive_indexes));
+		}
+	}
+#endif
 }
 
 /*