diff -up netpbm-10.47.09/converter/other/Makefile.lz netpbm-10.47.09/converter/other/Makefile
--- netpbm-10.47.09/converter/other/Makefile.lz	2010-02-18 09:09:34.000000000 +0100
+++ netpbm-10.47.09/converter/other/Makefile	2010-02-18 09:11:04.000000000 +0100
@@ -151,7 +151,7 @@ tifftopnm pamtotiff pnmtotiffcmyk: %: %.
 ifeq ($(shell libpng-config --version),)
   PNGLIB_LIBOPTS = $(shell $(LIBOPT) $(LIBOPTR) $(PNGLIB) $(ZLIB))
 else
-  PNGLIB_LIBOPTS = $(shell libpng-config --ldflags)
+  PNGLIB_LIBOPTS = $(shell libpng-config --ldflags) -lz
 endif
 
 pngtopnm pngtopam: %: %.o $(NETPBMLIB) $(LIBOPT)