diff --git a/libsolidity/formal/SMTPortfolio.cpp b/libsolidity/formal/SMTPortfolio.cpp
index 64806097e..8b9fe9ce1 100644
--- a/libsolidity/formal/SMTPortfolio.cpp
+++ b/libsolidity/formal/SMTPortfolio.cpp
@@ -29,6 +29,7 @@
 
 using namespace std;
 using namespace dev;
+using namespace dev::solidity;
 using namespace dev::solidity::smt;
 
 SMTPortfolio::SMTPortfolio(ReadCallback::Callback const& _readCallback)