diff --git a/src/backend/distributed/planner/multi_logical_optimizer.c b/src/backend/distributed/planner/multi_logical_optimizer.c
index e66b615f2..e56a00ab0 100644
--- a/src/backend/distributed/planner/multi_logical_optimizer.c
+++ b/src/backend/distributed/planner/multi_logical_optimizer.c
@@ -158,6 +158,7 @@ static Query * LateralQuery(Query *query);
 static bool SupportedLateralQuery(Query *parentQuery, Query *lateralQuery);
 static bool JoinOnPartitionColumn(Query *query);
 static void ErrorIfUnsupportedShardDistribution(Query *query);
+static List * RelationIdList(Query *query);
 static bool CoPartitionedTables(Oid firstRelationId, Oid secondRelationId);
 static bool ShardIntervalsEqual(FmgrInfo *comparisonFunction,
 								ShardInterval *firstInterval,
@@ -3861,7 +3862,7 @@ ErrorIfUnsupportedShardDistribution(Query *query)
 /*
  * RelationIdList returns list of unique relation ids in query tree.
  */
-List *
+static List *
 RelationIdList(Query *query)
 {
 	List *rangeTableList = NIL;
diff --git a/src/include/distributed/multi_logical_optimizer.h b/src/include/distributed/multi_logical_optimizer.h
index 9fc714698..810cc31bd 100644
--- a/src/include/distributed/multi_logical_optimizer.h
+++ b/src/include/distributed/multi_logical_optimizer.h
@@ -123,7 +123,6 @@ extern bool LeafQuery(Query *queryTree);
 extern List * PartitionColumnOpExpressionList(Query *query);
 extern List * ReplaceColumnsInOpExpressionList(List *opExpressionList, Var *newColumn);
 extern bool IsPartitionColumnRecursive(Expr *columnExpression, Query *query);
-extern List * RelationIdList(Query *query);
 
 
 #endif   /* MULTI_LOGICAL_OPTIMIZER_H */