diff --git a/src/rcldb/expansiondbs.h b/src/rcldb/expansiondbs.h
index e1f26244..2ed1bdcf 100644
--- a/src/rcldb/expansiondbs.h
+++ b/src/rcldb/expansiondbs.h
@@ -22,6 +22,8 @@
 
 #include <xapian.h>
 
+#include "unacpp.h"
+
 /** Specialization and overall creation code for the term expansion mechanism
  * defined in synfamily.h
  */