diff --git a/parse-options-cb.c b/parse-options-cb.c
index d346dbe210..4729277aa6 100644
--- a/parse-options-cb.c
+++ b/parse-options-cb.c
@@ -213,21 +213,6 @@ int parse_opt_noop_cb(const struct option *opt, const char *arg, int unset)
 	return 0;
 }
 
-/**
- * Report that the option is unknown, so that other code can handle
- * it. This can be used as a callback together with
- * OPTION_LOWLEVEL_CALLBACK to allow an option to be documented in the
- * "-h" output even if it's not being handled directly by
- * parse_options().
- */
-enum parse_opt_result parse_opt_unknown_cb(struct parse_opt_ctx_t *ctx,
-					   const struct option *opt,
-					   const char *arg, int unset)
-{
-	BUG_ON_OPT_ARG(arg);
-	return PARSE_OPT_UNKNOWN;
-}
-
 /**
  * Recreates the command-line option in the strbuf.
  */
diff --git a/parse-options.h b/parse-options.h
index 50d852f299..60b0a758d6 100644
--- a/parse-options.h
+++ b/parse-options.h
@@ -348,9 +348,6 @@ int parse_opt_commit(const struct option *, const char *, int);
 int parse_opt_tertiary(const struct option *, const char *, int);
 int parse_opt_string_list(const struct option *, const char *, int);
 int parse_opt_noop_cb(const struct option *, const char *, int);
-enum parse_opt_result parse_opt_unknown_cb(struct parse_opt_ctx_t *ctx,
-					   const struct option *,
-					   const char *, int);
 int parse_opt_passthru(const struct option *, const char *, int);
 int parse_opt_passthru_argv(const struct option *, const char *, int);
 /* value is enum branch_track* */