diff --git a/ir/constant.cpp b/ir/constant.cpp
index fe099c8a7..5a3dee67c 100644
--- a/ir/constant.cpp
+++ b/ir/constant.cpp
@@ -12,7 +12,7 @@
 #include <iomanip>
 #include <sstream>
 
-using namespace st;
+using namespace smt;
 using namespace std;
 using namespace util;