diff --git a/django/db/models/sql/compiler.py b/django/db/models/sql/compiler.py
index f6b6bba1d9..a68f6e0290 100644
--- a/django/db/models/sql/compiler.py
+++ b/django/db/models/sql/compiler.py
@@ -897,8 +897,11 @@ class SQLInsertCompiler(SQLCompiler):
             col = "%s.%s" % (qn(opts.db_table), qn(opts.pk.column))
             result.append("VALUES (%s)" % ", ".join(placeholders[0]))
             r_fmt, r_params = self.connection.ops.return_insert_id()
-            result.append(r_fmt % col)
-            params += r_params
+            # Skip empty r_fmt to allow subclasses to customize behaviour for
+            # 3rd party backends. Refs #19096.
+            if r_fmt:
+                result.append(r_fmt % col)
+                params += r_params
             return [(" ".join(result), tuple(params))]
         if can_bulk:
             result.append(self.connection.ops.bulk_insert_sql(fields, len(values)))