diff --git a/src/format/NXmxFormat.cpp b/src/format/NXmxFormat.cpp
index 177bd7d..d9d29e4 100644
--- a/src/format/NXmxFormat.cpp
+++ b/src/format/NXmxFormat.cpp
@@ -7,7 +7,7 @@
 #include "../H5Format.hpp"
 
 using namespace std;
-using s_ptr = s_ptr;
+using s_ptr = shared_ptr<h5_base>;
 
 class NXmxFormat : public H5Format
 {