diff --git a/Documentation/technical/api-parse-options.txt b/Documentation/technical/api-parse-options.txt
index 20b44ff9f32df79f64f2513f21777bf591d1c843..e66ca9f70c705841c864196a3a651e04d8156e01 100644
--- a/Documentation/technical/api-parse-options.txt
+++ b/Documentation/technical/api-parse-options.txt
@@ -96,7 +96,8 @@ Flags are the bitwise-or of:
 	`PARSE_OPT_STOP_AT_NON_OPTION` is set, the second argument in
 	`--unknown value` will be mistakenly interpreted as a
 	non-option, not as a value belonging to the unknown option,
-	stopping the parser early.
+	the parser early.  That's why parse_options() errors out if
+	both options are set.
 
 `PARSE_OPT_NO_INTERNAL_HELP`::
 	By default, parse_options() handles `-h`, `--help` and
diff --git a/parse-options.c b/parse-options.c
index 51e804b3bea3dab71e1df7b9c7db3635025b538e..cf71bcffd2e1e9aeacb44df488b0825f09d54255 100644
--- a/parse-options.c
+++ b/parse-options.c
@@ -244,6 +244,9 @@ void parse_options_start(struct parse_opt_ctx_t *ctx,
 	ctx->out  = argv;
 	ctx->cpidx = ((flags & PARSE_OPT_KEEP_ARGV0) != 0);
 	ctx->flags = flags;
+	if ((flags & PARSE_OPT_KEEP_UNKNOWN) &&
+	    (flags & PARSE_OPT_STOP_AT_NON_OPTION))
+		die("STOP_AT_NON_OPTION and KEEP_UNKNOWN don't go together");
 }
 
 static int usage_with_options_internal(const char * const *,