diff --git a/src/runtime/c/pgf/linearizer.h b/src/runtime/c/pgf/linearizer.h
index 6aeffb4e0..9d2d607ee 100644
--- a/src/runtime/c/pgf/linearizer.h
+++ b/src/runtime/c/pgf/linearizer.h
@@ -2,6 +2,7 @@
 #define PGF_LINEARIZER_H_
 
 #include <gu/enum.h>
+#include <pgf/data.h>
 
 /// Linearization of abstract syntax trees.