diff --git a/Makefile b/Makefile

index 2228844..4d4cc2c 100644

--- a/Makefile

+++ b/Makefile

@@ -21,19 +21,19 @@ shared relocatable: build_library_type/relocatable

 build_library_type/%: generate_sources do_links

 	@echo "====== Building $(@F) libraries ======"

-	${GPRBUILD} -m -j${PROCESSORS} -XLIBRARY_TYPE=$(@F) -Pgnatcoll_build -p

+	${GPRBUILD} -m -j${PROCESSORS} -XLIBRARY_TYPE=$(@F) -Pgnatcoll_build -p ${GNAT_OPTFLAGS}

 	@# Need to build libgnatcoll_gtk separately, because its project files

 	@# requires gtkada.gpr, which might not exist on the machine.

 ifeq (${WITH_GTK},yes)

-	${GPRBUILD} -m -j${PROCESSORS} -XLIBRARY_TYPE=$(@F) -Psrc/gnatcoll_gtk -p

+	${GPRBUILD} -m -j${PROCESSORS} -XLIBRARY_TYPE=$(@F) -Psrc/gnatcoll_gtk -p ${GNAT_OPTFLAGS}

 endif

 	@# Build the tools (the list is the project's Main attribute)

 	@# They are not build as part of the above because only the Main from

 	@# gnatcoll_build.gpr are build. We could use aggregate projects to speed

 	@# things up.

-	${GPRBUILD} -q -m -j${PROCESSORS} -XLIBRARY_TYPE=$(@F) -Psrc/gnatcoll_tools

+	${GPRBUILD} -q -m -j${PROCESSORS} -XLIBRARY_TYPE=$(@F) -Psrc/gnatcoll_tools ${GNAT_OPTFLAGS}

 # Regenerate part of the sources. Unfortunately, this can be run only after

 # we have build GNATCOLL, and then its tools, even though GNATCOLL itself