diff -up cfitsio/Makefile.in.orig cfitsio/Makefile.in
--- cfitsio/Makefile.in.orig	2012-04-11 13:55:24.000000000 -0600
+++ cfitsio/Makefile.in	2012-04-13 10:07:54.549874768 -0600
@@ -87,7 +87,7 @@ libcfitsio.a:	${OBJECTS}
 shared: libcfitsio${SHLIB_SUFFIX}
 
 libcfitsio${SHLIB_SUFFIX}: ${OBJECTS}
-		${SHLIB_LD} ${LDFLAGS} -o $@ ${OBJECTS}
+		${SHLIB_LD} ${LDFLAGS} -o $@ ${OBJECTS} -lm
 
 install:	libcfitsio.a $(INSTALL_DIRS)
 		@if [ -f libcfitsio.a ]; then \