diff --git a/Makefile-rpm-ostree.am b/Makefile-rpm-ostree.am
index a7a6e5a2..ece83897 100644
--- a/Makefile-rpm-ostree.am
+++ b/Makefile-rpm-ostree.am
@@ -32,7 +32,7 @@ rpm_ostree_SOURCES = src/app/main.cxx \
 	src/app/rpmostree-builtin-initramfs.c \
 	src/app/rpmostree-builtin-initramfs-etc.c \
 	src/app/rpmostree-builtin-livefs.c \
-	src/app/rpmostree-builtin-usroverlay.c \
+	src/app/rpmostree-builtin-usroverlay.cxx \
 	src/app/rpmostree-builtin-override.cxx \
 	src/app/rpmostree-builtin-refresh-md.c \
 	src/app/rpmostree-builtin-reset.cxx \
diff --git a/src/app/rpmostree-builtin-usroverlay.c b/src/app/rpmostree-builtin-usroverlay.cxx
similarity index 100%
rename from src/app/rpmostree-builtin-usroverlay.c
rename to src/app/rpmostree-builtin-usroverlay.cxx