diff --git a/libcorpus2/tag.h b/libcorpus2/tag.h
index 0f38f470417b4ef80bf73f732c3513b6c0d0d085..4407eba7212f29b8909a1de80610e839862c215e 100644
--- a/libcorpus2/tag.h
+++ b/libcorpus2/tag.h
@@ -152,7 +152,7 @@ public:
 	 * Boost seralization support. Users must include appropriate boost headers.
 	 */
 	template<class Archive>
-	void serialize(Archive & ar,const unsigned int version)
+	void serialize(Archive & ar, const unsigned int version)
 	{
 		ar & pos_;
 		ar & values_;