diff --git a/doc/Makefile.am b/doc/Makefile.am
index 00f4bfce..6c36469d 100644
--- a/doc/Makefile.am
+++ b/doc/Makefile.am
@@ -21,5 +21,5 @@ ocpasswd.8: ../src/ocpasswd-args.def
 	rm -f "$<".tmp
 
 install-data-local:
-	-test -d "$(DBUS_CONFIG_DIR)" && $(INSTALL_DATA) dbus/org.infradead.ocserv.conf $(DBUS_CONFIG_DIR)
-	-test -d "/usr/lib/systemd/system/" && $(INSTALL_DATA) systemd/standalone/ocserv.service /usr/lib/systemd/system/
+	-test -d "$(DBUS_CONFIG_DIR)" && ! test -f $(DBUS_CONFIG_DIR)/org.infradead.ocserv.conf && $(INSTALL_DATA) dbus/org.infradead.ocserv.conf $(DBUS_CONFIG_DIR)
+	-test -d "/usr/lib/systemd/system/" && ! test -f /usr/lib/systemd/system/ocserv.service && $(INSTALL_DATA) systemd/standalone/ocserv.service /usr/lib/systemd/system/