diff --git a/src/EquationTags.hh b/src/EquationTags.hh
index 34277baef41c7a09123cd8fbc9a9c1a5677dafdb..7db769b39ac0f5996aa34e2b3ac993af170fd767 100644
--- a/src/EquationTags.hh
+++ b/src/EquationTags.hh
@@ -20,12 +20,13 @@
 #ifndef _EQUATION_TAGS_HH
 #define _EQUATION_TAGS_HH
 
-using namespace std;
-
+#include <iostream>
 #include <map>
 #include <set>
 #include <string>
 
+using namespace std;
+
 class EquationTags
 {
 private: