diff --git a/src/graph-path-validation.cc b/src/graph-path-validation.cc
index 0073bbf6d320fc1bbf4dcd4ff0d4592b2d8dcaa6..c5d839be2ac9672c8b4f9d2886a13959a981a1e5 100644
--- a/src/graph-path-validation.cc
+++ b/src/graph-path-validation.cc
@@ -23,6 +23,10 @@
 #include <hpp/manipulation/graph/graph.hh>
 #include <hpp/manipulation/constraint-set.hh>
 
+#ifdef HPP_DEBUG
+# include <hpp/manipulation/graph/state.hh>
+#endif
+
 namespace hpp {
   namespace manipulation {
     GraphPathValidationPtr_t GraphPathValidation::create (const PathValidationPtr_t& pathValidation)