diff --git a/src/backend/executor/functions.c b/src/backend/executor/functions.c
index 0a1bb9d52eeaa42f62f75ab3237ea7932cc5c84e..039defa7b85f681f5398838b7946fd9941ce9402 100644
--- a/src/backend/executor/functions.c
+++ b/src/backend/executor/functions.c
@@ -500,7 +500,16 @@ init_execution_state(List *queryTree_list,
 						  fcache->readonly_func ? CURSOR_OPT_PARALLEL_OK : 0,
 											  NULL);
 
-			/* Precheck all commands for validity in a function */
+			/*
+			 * Precheck all commands for validity in a function.  This should
+			 * generally match the restrictions spi.c applies.
+			 */
+			if (IsA(stmt, CopyStmt) &&
+				((CopyStmt *) stmt)->filename == NULL)
+				ereport(ERROR,
+						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					errmsg("cannot COPY to/from client in a SQL function")));
+
 			if (IsA(stmt, TransactionStmt))
 				ereport(ERROR,
 						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),