diff --git a/src/backend/parser/analyze.c b/src/backend/parser/analyze.c
index 09c28dca03..76282f4009 100644
--- a/src/backend/parser/analyze.c
+++ b/src/backend/parser/analyze.c
@@ -25,6 +25,7 @@
 #include "postgres.h"
 
 #include "catalog/pg_type.h"
+#include "miscadmin.h"
 #include "nodes/makefuncs.h"
 #include "optimizer/clauses.h"
 #include "optimizer/var.h"
@@ -1238,6 +1239,9 @@ transformSetOperationTree(ParseState *pstate, SelectStmt *stmt)
 
 	Assert(stmt && IsA(stmt, SelectStmt));
 
+	/* Guard against stack overflow due to overly complex set-expressions */
+	check_stack_depth();
+
 	/*
 	 * Validity-check both leaf and internal SELECTs for disallowed ops.
 	 */