diff --git a/src/image_compositing.cpp b/src/image_compositing.cpp
index a8f9bba3c..d6c8a3333 100644
--- a/src/image_compositing.cpp
+++ b/src/image_compositing.cpp
@@ -191,7 +191,20 @@ struct composite_visitor
           dy_(dy) {}
 
     template <typename T>
-    void operator() (T & dst) const;
+    void operator() (T & dst) const
+    {
+        throw std::runtime_error("Error: Composite with " + std::string(typeid(dst).name()) + " is not supported");
+    }
+
+    void operator()(image_rgba8 & dst) const
+    {
+        composite(dst, util::get<image_rgba8>(src_), mode_, opacity_, dx_, dy_);
+    }
+
+    void operator() (image_gray32f & dst) const
+    {
+        composite(dst, util::get<image_gray32f>(src_), mode_, opacity_, dx_, dy_);
+    }
 
   private:
     image_any const& src_;
@@ -199,26 +212,9 @@ struct composite_visitor
     float opacity_;
     int dx_;
     int dy_;
+
 };
 
-template <typename T>
-void composite_visitor::operator() (T & dst) const
-{
-    throw std::runtime_error("Error: Composite with " + std::string(typeid(dst).name()) + " is not supported");
-}
-
-template <>
-void composite_visitor::operator()<image_rgba8> (image_rgba8 & dst) const
-{
-    composite(dst, util::get<image_rgba8>(src_), mode_, opacity_, dx_, dy_);
-}
-
-template <>
-void composite_visitor::operator()<image_gray32f> (image_gray32f & dst) const
-{
-    composite(dst, util::get<image_gray32f>(src_), mode_, opacity_, dx_, dy_);
-}
-
 } // end ns
 
 template <>