diff --git a/include/plasp/pddl/translation/Predicate.h b/include/plasp/pddl/translation/Predicate.h
index 2fb380d..ef3eabe 100644
--- a/include/plasp/pddl/translation/Predicate.h
+++ b/include/plasp/pddl/translation/Predicate.h
@@ -2,6 +2,7 @@
 #define __PLASP__PDDL__TRANSLATION__PREDICATE_H
 
 #include <plasp/output/Formatting.h>
+#include <plasp/pddl/expressions/Constant.h>
 #include <plasp/pddl/expressions/DerivedPredicate.h>
 #include <plasp/pddl/expressions/Predicate.h>
 #include <plasp/pddl/expressions/PredicateDeclaration.h>