diff --git a/clients/cli/utils.c b/clients/cli/utils.c
index 727e309d1c..ce4749bfd1 100644
--- a/clients/cli/utils.c
+++ b/clients/cli/utils.c
@@ -517,6 +517,36 @@ nmc_string_to_bool (const char *str, gboolean *val_bool, GError **error)
 	return TRUE;
 }
 
+gboolean
+nmc_string_to_tristate (const char *str, NMCTriStateValue *val, GError **error)
+{
+	const char *s_true[] = { "true", "yes", "on", NULL };
+	const char *s_false[] = { "false", "no", "off", NULL };
+	const char *s_unknown[] = { "unknown", NULL };
+
+	g_return_val_if_fail (error == NULL || *error == NULL, FALSE);
+
+	if (g_strcmp0 (str, "o") == 0) {
+		g_set_error (error, 1, 0,
+		             _("'%s' is ambiguous (on x off)"), str);
+		return FALSE;
+	}
+
+	if (nmc_string_is_valid (str, s_true, NULL))
+		*val = NMC_TRI_STATE_YES;
+	else if (nmc_string_is_valid (str, s_false, NULL))
+		*val = NMC_TRI_STATE_NO;
+	else if (nmc_string_is_valid (str, s_unknown, NULL))
+		*val = NMC_TRI_STATE_UNKNOWN;
+	else {
+		g_set_error (error, 1, 0,
+		             _("'%s' is not valid; use [%s], [%s] or [%s]"),
+		             str, "true, yes, on", "false, no, off", "unknown");
+		return FALSE;
+	}
+	return TRUE;
+}
+
 /*
  * Ask user for input and return the string.
  * The caller is responsible for freeing the returned string.
diff --git a/clients/cli/utils.h b/clients/cli/utils.h
index 6defb1de14..54f76b071a 100644
--- a/clients/cli/utils.h
+++ b/clients/cli/utils.h
@@ -32,6 +32,12 @@ typedef struct {
 	gboolean found;
 } nmc_arg_t;
 
+typedef enum {
+	NMC_TRI_STATE_NO,
+	NMC_TRI_STATE_YES,
+	NMC_TRI_STATE_UNKNOWN,
+} NMCTriStateValue;
+
 /* === Functions === */
 int matches (const char *cmd, const char *pattern);
 int next_arg (int *argc, char ***argv);
@@ -62,6 +68,7 @@ gboolean nmc_string_to_uint (const char *str,
                              unsigned long int max,
                              unsigned long int *value);
 gboolean nmc_string_to_bool (const char *str, gboolean *val_bool, GError **error);
+gboolean nmc_string_to_tristate (const char *str, NMCTriStateValue *val, GError **error);
 char *nmc_ip4_address_as_string (guint32 ip, GError **error);
 char *nmc_ip6_address_as_string (const struct in6_addr *ip, GError **error);
 void nmc_terminal_erase_line (void);