diff --git a/src/libnm-glib-aux/nm-shared-utils.h b/src/libnm-glib-aux/nm-shared-utils.h
index 8ca65a796a..82af7a052f 100644
--- a/src/libnm-glib-aux/nm-shared-utils.h
+++ b/src/libnm-glib-aux/nm-shared-utils.h
@@ -18,6 +18,8 @@ typedef enum _nm_packed {
     NM_OPTION_BOOL_TRUE    = 1,
 } NMOptionBool;
 
+#define nm_assert_is_ternary(value) nm_assert(NM_IN_SET((value), -1, 0, 1))
+
 /*****************************************************************************/
 
 static inline gboolean