diff --git a/eo/src/eoFixedLength.h b/eo/src/eoFixedLength.h
index b57e0733..a7355e5b 100644
--- a/eo/src/eoFixedLength.h
+++ b/eo/src/eoFixedLength.h
@@ -60,7 +60,7 @@ class eoFixedLength : public EO<FitT>, public std::vector<GeneType>
 
         os << size() << ' ';
 
-        std::copy(begin(), end(), ostream_iterator<double>(os, " "));
+        std::copy(begin(), end(), ostream_iterator<AtomType>(os, " "));
     }
 
     /// reading...