diff --git a/pam_rd/Makefile.am b/pam_rd/Makefile.am
index 05de5a93..79bcf0ed 100644
--- a/pam_rd/Makefile.am
+++ b/pam_rd/Makefile.am
@@ -29,8 +29,9 @@ MOC = @QT_MOC@
 moc_%.cpp:	%.h
 	$(MOC) $< -o $@
 
+inst_prefix_dir=$(DESTDIR)
 inst_lib_LTLIBRARIES = pam_rd.la
-inst_libdir=/@RD_LIB_PATH@/security
+inst_libdir=$(prefix)/@RD_LIB_PATH@/security
 dist_pam_rd_la_SOURCES = pam_rd.cpp
 pam_rd_la_LDFLAGS = -module -shared -Xlinker -x -avoid-version -export-dynamic
 pam_rd_la_LIBADD = @LIB_RDLIBS@ -lpam @LIBVORBIS@