diff --git a/src/libnm-core-impl/nm-setting-ovs-external-ids.c b/src/libnm-core-impl/nm-setting-ovs-external-ids.c
index f4e31f81c..44bb1d3e6 100644
--- a/src/libnm-core-impl/nm-setting-ovs-external-ids.c
+++ b/src/libnm-core-impl/nm-setting-ovs-external-ids.c
@@ -53,15 +53,6 @@ G_DEFINE_TYPE(NMSettingOvsExternalIDs, nm_setting_ovs_external_ids, NM_TYPE_SETT
 
 /*****************************************************************************/
 
-static gboolean
-_exid_key_char_is_regular(char ch)
-{
-    /* allow words of printable characters, plus some
-     * special characters, for example to support base64 encoding. */
-    return (ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z') || (ch >= '0' && ch <= '9')
-           || NM_IN_SET(ch, '-', '_', '+', '/', '=', '.');
-}
-
 /**
  * nm_setting_ovs_external_ids_check_key:
  * @key: (allow-none): the key to check
@@ -105,7 +96,7 @@ nm_setting_ovs_external_ids_check_key(const char *key, GError **error)
                             _("key must be UTF8"));
         return FALSE;
     }
-    if (!NM_STRCHAR_ALL(key, ch, _exid_key_char_is_regular(ch))) {
+    if (!NM_STRCHAR_ALL(key, ch, nm_ascii_is_regular_char(ch))) {
         /* Probably OVS is more forgiving about what makes a valid key for
          * an external-id. However, we are strict (at least, for now). */
         g_set_error_literal(error,
diff --git a/src/libnm-glib-aux/nm-macros-internal.h b/src/libnm-glib-aux/nm-macros-internal.h
index 974355b26..71a17e3e3 100644
--- a/src/libnm-glib-aux/nm-macros-internal.h
+++ b/src/libnm-glib-aux/nm-macros-internal.h
@@ -1101,6 +1101,32 @@ nm_ascii_is_newline(char ch)
     return NM_IN_SET(ch, '\n', '\t');
 }
 
+static inline gboolean
+nm_ascii_is_regular_char(char ch)
+{
+    /* Checks whether "ch" is "regular", which basically
+     * means it's either a digit, a alpha, or some special
+     * characters that are suitable for base64 encoding.
+     *
+     * The meaning of what "regular" means is not well defined,
+     * but it's used to validate the keys for "ovs.external-ids"
+     * dictionary. */
+    switch (ch) {
+    case 'a' ... 'z':
+    case 'A' ... 'Z':
+    case '0' ... '9':
+    case '-':
+    case '_':
+    case '+':
+    case '/':
+    case '=':
+    case '.':
+        return TRUE;
+    default:
+        return FALSE;
+    }
+}
+
 #define nm_str_skip_leading_spaces(str)                          \
     ({                                                           \
         typeof(*(str))              *_str_sls        = (str);    \