diff --git a/libnm-core/nm-core-internal.h b/libnm-core/nm-core-internal.h
index 01b3a55db6..afdd2f2fc1 100644
--- a/libnm-core/nm-core-internal.h
+++ b/libnm-core/nm-core-internal.h
@@ -230,6 +230,24 @@ _NM_SETTING_WIRED_WAKE_ON_LAN_CAST(NMSettingWiredWakeOnLan v)
 
 /*****************************************************************************/
 
+static inline NMTernary
+NM_TERNARY_FROM_OPTION_BOOL(NMOptionBool v)
+{
+    nm_assert(NM_IN_SET(v, NM_OPTION_BOOL_DEFAULT, NM_OPTION_BOOL_TRUE, NM_OPTION_BOOL_FALSE));
+
+    return (NMTernary) v;
+}
+
+static inline NMOptionBool
+NM_TERNARY_TO_OPTION_BOOL(NMTernary v)
+{
+    nm_assert(NM_IN_SET(v, NM_TERNARY_DEFAULT, NM_TERNARY_TRUE, NM_TERNARY_FALSE));
+
+    return (NMOptionBool) v;
+}
+
+/*****************************************************************************/
+
 typedef enum { /*< skip >*/
                NM_SETTING_PARSE_FLAGS_NONE        = 0,
                NM_SETTING_PARSE_FLAGS_STRICT      = 1LL << 0,
diff --git a/shared/nm-glib-aux/nm-shared-utils.h b/shared/nm-glib-aux/nm-shared-utils.h
index 669c9fbcb4..8f0d50c9f5 100644
--- a/shared/nm-glib-aux/nm-shared-utils.h
+++ b/shared/nm-glib-aux/nm-shared-utils.h
@@ -8,6 +8,18 @@
 
 #include <netinet/in.h>
 
+/*****************************************************************************/
+
+/* An optional boolean (like NMTernary, with identical numerical
+ * enum values). Note that this enum type is _nm_packed! */
+typedef enum _nm_packed {
+    NM_OPTION_BOOL_DEFAULT = -1,
+    NM_OPTION_BOOL_FALSE   = 0,
+    NM_OPTION_BOOL_TRUE    = 1,
+} NMOptionBool;
+
+/*****************************************************************************/
+
 static inline gboolean
 nm_is_ascii(char ch)
 {