diff --git a/src/ass_attachment.cpp b/src/ass_attachment.cpp
index 6f5bd3a08..5fd79c06d 100644
--- a/src/ass_attachment.cpp
+++ b/src/ass_attachment.cpp
@@ -22,6 +22,8 @@
 
 #include <boost/algorithm/string/predicate.hpp>
 
+AssEntryGroup AssAttachment::Group() const { return group; }
+
 AssAttachment::AssAttachment(AssAttachment const& rgt)
 : entry_data(rgt.entry_data)
 , filename(rgt.filename)
diff --git a/src/ass_attachment.h b/src/ass_attachment.h
index 34416d674..1f583a614 100644
--- a/src/ass_attachment.h
+++ b/src/ass_attachment.h
@@ -46,7 +46,7 @@ public:
 	std::string GetFileName(bool raw=false) const;
 
 	std::string const& GetEntryData() const { return entry_data; }
-	AssEntryGroup Group() const override { return group; }
+	AssEntryGroup Group() const override;
 
 	AssAttachment(AssAttachment const& rgt);
 	AssAttachment(std::string const& header, AssEntryGroup group);