diff --git a/Lib/Makefile.am b/Lib/Makefile.am
index 58fe8a0a..fe6504f5 100644
--- a/Lib/Makefile.am
+++ b/Lib/Makefile.am
@@ -1 +1 @@
-SUBDIRS = Bucket DEM XGL
+SUBDIRS = Bucket Debug DEM Math XGL zlib
diff --git a/Lib/Makefile.in b/Lib/Makefile.in
index 1a8fd3a9..e9b0a93c 100644
--- a/Lib/Makefile.in
+++ b/Lib/Makefile.in
@@ -71,7 +71,7 @@ PACKAGE = @PACKAGE@
 RANLIB = @RANLIB@
 VERSION = @VERSION@
 
-SUBDIRS = Bucket DEM XGL
+SUBDIRS = Bucket Debug DEM Math XGL zlib
 mkinstalldirs = $(SHELL) $(top_srcdir)/mkinstalldirs
 CONFIG_HEADER = ../Include/config.h
 CONFIG_CLEAN_FILES =