diff --git a/src/ass_style.cpp b/src/ass_style.cpp
index e82514653..45072b943 100644
--- a/src/ass_style.cpp
+++ b/src/ass_style.cpp
@@ -50,6 +50,8 @@ AssStyle::AssStyle() {
 	UpdateData();
 }
 
+AssEntryGroup AssStyle::Group() const { return AssEntryGroup::STYLE; }
+
 namespace {
 class parser {
 	boost::split_iterator<agi::StringRange::const_iterator> pos;
diff --git a/src/ass_style.h b/src/ass_style.h
index 1ec57073e..bbbf94787 100644
--- a/src/ass_style.h
+++ b/src/ass_style.h
@@ -74,7 +74,7 @@ public:
 	AssStyle(std::string const& data, int version=1);
 
 	std::string const& GetEntryData() const { return data; }
-	AssEntryGroup Group() const override { return AssEntryGroup::STYLE; }
+	AssEntryGroup Group() const override;
 
 	/// Convert an ASS alignment to the equivalent SSA alignment
 	static int AssToSsa(int ass_align);