diff --git a/libsolidity/formal/SymbolicState.cpp b/libsolidity/formal/SymbolicState.cpp
index 6801e7717..3b613b75f 100644
--- a/libsolidity/formal/SymbolicState.cpp
+++ b/libsolidity/formal/SymbolicState.cpp
@@ -28,6 +28,7 @@
 
 using namespace std;
 using namespace solidity;
+using namespace solidity::util;
 using namespace solidity::smtutil;
 using namespace solidity::frontend::smt;