diff --git a/src/google/protobuf/testdata/extdecl/dup_number/extdecl_field_options.txtpb b/src/google/protobuf/testdata/extdecl/dup_number/extdecl_field_options.txtpb
new file mode 100644
index 0000000000000..030f6e657587e
--- /dev/null
+++ b/src/google/protobuf/testdata/extdecl/dup_number/extdecl_field_options.txtpb
@@ -0,0 +1,14 @@
+# For Protobuf extension declaration test only.
+# DO NOT add extension declaration to this file.
+
+declaration {
+  number: 525000000
+  full_name: ".protoc.extension.declaration.test.foo"
+  type: "string"
+}
+
+declaration {
+  number: 525000000
+  full_name: ".protoc.extension.declaration.test.bar"
+  type: "string"
+}