diff --git a/cache.h b/cache.h
index 18fdd18f36..0e8e5d8002 100644
--- a/cache.h
+++ b/cache.h
@@ -1136,6 +1136,9 @@ extern int check_repository_format_version(const char *var, const char *value, v
 extern int git_env_bool(const char *, int);
 extern int git_config_system(void);
 extern int config_error_nonbool(const char *);
+#ifdef __GNUC__
+#define config_error_nonbool(s) (config_error_nonbool(s), -1)
+#endif
 extern const char *get_log_output_encoding(void);
 extern const char *get_commit_output_encoding(void);
 
diff --git a/config.c b/config.c
index fb3f8681ee..526f682374 100644
--- a/config.c
+++ b/config.c
@@ -1660,6 +1660,7 @@ int git_config_rename_section(const char *old_name, const char *new_name)
  * Call this to report error for your variable that should not
  * get a boolean value (i.e. "[my] var" means "true").
  */
+#undef config_error_nonbool
 int config_error_nonbool(const char *var)
 {
 	return error("Missing value for '%s'", var);
diff --git a/parse-options.c b/parse-options.c
index c1c66bd408..67e98a6323 100644
--- a/parse-options.c
+++ b/parse-options.c
@@ -18,15 +18,6 @@ int optbug(const struct option *opt, const char *reason)
 	return error("BUG: switch '%c' %s", opt->short_name, reason);
 }
 
-int opterror(const struct option *opt, const char *reason, int flags)
-{
-	if (flags & OPT_SHORT)
-		return error("switch `%c' %s", opt->short_name, reason);
-	if (flags & OPT_UNSET)
-		return error("option `no-%s' %s", opt->long_name, reason);
-	return error("option `%s' %s", opt->long_name, reason);
-}
-
 static int get_arg(struct parse_opt_ctx_t *p, const struct option *opt,
 		   int flags, const char **arg)
 {
@@ -594,3 +585,12 @@ static int parse_options_usage(struct parse_opt_ctx_t *ctx,
 	return usage_with_options_internal(ctx, usagestr, opts, 0, err);
 }
 
+#undef opterror
+int opterror(const struct option *opt, const char *reason, int flags)
+{
+	if (flags & OPT_SHORT)
+		return error("switch `%c' %s", opt->short_name, reason);
+	if (flags & OPT_UNSET)
+		return error("option `no-%s' %s", opt->long_name, reason);
+	return error("option `%s' %s", opt->long_name, reason);
+}
diff --git a/parse-options.h b/parse-options.h
index 71a39c60d9..e703853749 100644
--- a/parse-options.h
+++ b/parse-options.h
@@ -177,6 +177,10 @@ extern NORETURN void usage_msg_opt(const char *msg,
 
 extern int optbug(const struct option *opt, const char *reason);
 extern int opterror(const struct option *opt, const char *reason, int flags);
+#ifdef __GNUC__
+#define opterror(o,r,f) (opterror((o),(r),(f)), -1)
+#endif
+
 /*----- incremental advanced APIs -----*/
 
 enum {