diff --git a/meson.build b/meson.build
index 0873349d3..d582a5cd5 100644
--- a/meson.build
+++ b/meson.build
@@ -483,6 +483,7 @@ endif
 gnome = import('gnome')
 i18n = import('i18n')
 
+conf.set_quoted('FWUPD_PREFIX', prefix)
 conf.set_quoted('FWUPD_BINDIR', bindir)
 conf.set_quoted('FWUPD_LIBDIR', libdir)
 conf.set_quoted('FWUPD_LIBEXECDIR', libexecdir)
diff --git a/plugins/redfish/fu-self-test.c b/plugins/redfish/fu-self-test.c
index 4710c7697..c507fabc8 100644
--- a/plugins/redfish/fu-self-test.c
+++ b/plugins/redfish/fu-self-test.c
@@ -27,7 +27,7 @@ fu_test_is_installed_test(void)
 	const gchar *builddir = g_getenv("G_TEST_BUILDDIR");
 	if (builddir == NULL)
 		return FALSE;
-	return g_str_has_prefix(builddir, "/usr");
+	return g_str_has_prefix(builddir, FWUPD_PREFIX);
 }
 
 static void