diff --git a/doc/src/sgml/spi.sgml b/doc/src/sgml/spi.sgml
index 5ff79dc5d9a..036c552a1ac 100644
--- a/doc/src/sgml/spi.sgml
+++ b/doc/src/sgml/spi.sgml
@@ -2083,6 +2083,19 @@ Portal SPI_cursor_find(const char * <parameter>name</parameter>)
    <symbol>NULL</symbol> if none was found
   </para>
  </refsect1>
+
+ <refsect1>
+  <title>Notes</title>
+
+  <para>
+   Beware that this function can return a <type>Portal</type> object
+   that does not have cursor-like properties; for example it might not
+   return tuples.  If you simply pass the <type>Portal</type> pointer
+   to other SPI functions, they can defend themselves against such
+   cases, but caution is appropriate when directly inspecting
+   the <type>Portal</type>.
+  </para>
+ </refsect1>
 </refentry>
 
 <!-- *********************************************** -->
diff --git a/src/backend/utils/adt/xml.c b/src/backend/utils/adt/xml.c
index fd197c6d219..1c8f1b5c4ad 100644
--- a/src/backend/utils/adt/xml.c
+++ b/src/backend/utils/adt/xml.c
@@ -2745,6 +2745,10 @@ cursor_to_xmlschema(PG_FUNCTION_ARGS)
 		ereport(ERROR,
 				(errcode(ERRCODE_UNDEFINED_CURSOR),
 				 errmsg("cursor \"%s\" does not exist", name)));
+	if (portal->tupDesc == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_CURSOR_STATE),
+				 errmsg("portal \"%s\" does not return tuples", name)));
 
 	xmlschema = _SPI_strdup(map_sql_table_to_xmlschema(portal->tupDesc,
 													   InvalidOid, nulls,