diff --git a/vhdlpp/expression.cc b/vhdlpp/expression.cc
index 76f089bcb..390e18b3b 100644
--- a/vhdlpp/expression.cc
+++ b/vhdlpp/expression.cc
@@ -27,6 +27,7 @@
 using namespace std;
 
 Expression::Expression()
+: type_(0)
 {
 }