--- a/Makefile	2012-07-17 11:27:16.291596708 +0400
+++ b/Makefile	2012-07-17 11:27:44.800595858 +0400
@@ -91,7 +91,7 @@
 install_library_type:
 	${MKDIR} ${bindir}
 	${MKDIR} ${libdir}/${TARNAME}/${LIBRARY_TYPE}
-	${MKDIR} ${DESTDIR}${prefix}/lib/gnat/${TARNAME}
+	${MKDIR} ${DESTDIR}${projectdir}/${TARNAME}
 	${MKDIR} ${datadir}/examples
 	${MKDIR} ${datadir}/gnatcoll
 	${MKDIR} ${includedir}/${TARNAME}
@@ -111,7 +111,7 @@
 	${CP} src/dborm.py ${datadir}/gnatcoll/
 	${CP} distrib/gnatcoll_gps.xml ${datadir}/gps/plug-ins
 	${CP} distrib/gnatcoll_runtime.xml ${datadir}/gps/plug-ins
-	${CP} distrib/*.gpr ${DESTDIR}${prefix}/lib/gnat
+	${CP} distrib/*.gpr ${DESTDIR}${projectdir}/
 
 install_docs:
 	${MKDIR} ${datadir}/doc/gnatcoll/html
--- a/Makefile.conf.in	2012-07-17 11:27:47.783595765 +0400
+++ b/Makefile.conf.in	2012-07-17 11:28:39.584594273 +0400
@@ -43,6 +43,7 @@
 bindir=${DESTDIR}@bindir@
 libdir=${DESTDIR}@libdir@
 includedir=${DESTDIR}@includedir@
+projectdir ?= ${prefix}/lib/gnat
 
 MKDIR=mkdir -p
 CP=cp -p
@@ -151,9 +152,9 @@
 installsources:
 	@${CP} -p ${wildcard ${addsuffix *.ad[bs], ${SRCDIRS}}} ${includedir}/${TARNAME}
 ifeq (${OS},Windows_NT)
-	@cd ${includedir}/${TARNAME}; ls ${notdir ${wildcard ${addsuffix *.ad[bs], ${SRCDIRS}}}} | grep -v unix > ${DESTDIR}${prefix}/lib/gnat/${TARNAME}/${basename ${PROJECT}}.lgpr
+	@cd ${includedir}/${TARNAME}; ls ${notdir ${wildcard ${addsuffix *.ad[bs], ${SRCDIRS}}}} | grep -v unix > ${DESTDIR}${projectdir}/${TARNAME}/${basename ${PROJECT}}.lgpr
 else
-	@cd ${includedir}/${TARNAME}; ls ${notdir ${wildcard ${addsuffix *.ad[bs], ${SRCDIRS}}}} | grep -v win32 > ${DESTDIR}${prefix}/lib/gnat/${TARNAME}/${basename ${PROJECT}}.lgpr
+	@cd ${includedir}/${TARNAME}; ls ${notdir ${wildcard ${addsuffix *.ad[bs], ${SRCDIRS}}}} | grep -v win32 > ${DESTDIR}${projectdir}/${TARNAME}/${basename ${PROJECT}}.lgpr
 endif
 
 force: