diff --git a/core/include/prometheus/detail/builder.h b/core/include/prometheus/detail/builder.h
index 5e45755e..0278d993 100644
--- a/core/include/prometheus/detail/builder.h
+++ b/core/include/prometheus/detail/builder.h
@@ -3,8 +3,6 @@
 #include <map>
 #include <string>
 
-//#include "prometheus/registry.h"
-
 namespace prometheus {
 
 template <typename T>
diff --git a/core/src/detail/builder.cc b/core/src/detail/builder.cc
index 17b01c47..ac285205 100644
--- a/core/src/detail/builder.cc
+++ b/core/src/detail/builder.cc
@@ -34,5 +34,10 @@ Family<T>& Builder<T>::Register(Registry& registry) {
   return registry.Add<T>(name_, help_, labels_);
 }
 
+template class Builder<Counter>;
+template class Builder<Gauge>;
+template class Builder<Histogram>;
+template class Builder<Summary>;
+
 }  // namespace detail
 }  // namespace prometheus