diff --git a/lemon/Makefile.am b/lemon/Makefile.am
--- a/lemon/Makefile.am
+++ b/lemon/Makefile.am
@@ -16,9 +16,10 @@
 
 lemon_HEADERS += \
         lemon/dim2.h \
+	lemon/error.h \
+	lemon/list_graph.h \
 	lemon/maps.h \
         lemon/random.h \
-	lemon/list_graph.h \
         lemon/tolerance.h
 
 bits_HEADERS += \