diff --git a/include/aidge/data/Data.hpp b/include/aidge/data/Data.hpp
index cd7581acfa1f31b68a9275d08a82e70bca4353ee..b73c3977f6a3319866dd0954221ad23ae2b20151 100644
--- a/include/aidge/data/Data.hpp
+++ b/include/aidge/data/Data.hpp
@@ -56,8 +56,6 @@ public:
 private:
     const char* mType;
 };
-
-inline auto format_as(DataType dt) { return EnumStrings<Aidge::DataType>::data[static_cast<int>(dt)]; }
 }
 
 namespace {
@@ -82,4 +80,8 @@ const char* const EnumStrings<Aidge::DataType>::data[]
        "UInt7", "UInt8", "UInt16", "UInt32", "UInt64"};
 }
 
+namespace Aidge {
+inline auto format_as(DataType dt) { return EnumStrings<Aidge::DataType>::data[static_cast<int>(dt)]; }
+}
+
 #endif /* AIDGE_DATA_H_ */
\ No newline at end of file