diff --git a/diff.c b/diff.c
index 4a350e365e..f0985bc76a 100644
--- a/diff.c
+++ b/diff.c
@@ -3737,6 +3737,12 @@ void diffcore_fix_diff_index(struct diff_options *options)
 
 void diffcore_std(struct diff_options *options)
 {
+	/* We never run this function more than one time, because the
+	 * rename/copy detection logic can only run once.
+	 */
+	if (diff_queued_diff.run)
+		return;
+
 	if (options->skip_stat_unmatch)
 		diffcore_skip_stat_unmatch(options);
 	if (options->break_opt != -1)
@@ -3756,6 +3762,8 @@ void diffcore_std(struct diff_options *options)
 		DIFF_OPT_SET(options, HAS_CHANGES);
 	else
 		DIFF_OPT_CLR(options, HAS_CHANGES);
+
+	diff_queued_diff.run = 1;
 }
 
 int diff_result_code(struct diff_options *opt, int status)
diff --git a/diffcore.h b/diffcore.h
index 5d05deaf68..491bea0b44 100644
--- a/diffcore.h
+++ b/diffcore.h
@@ -91,11 +91,13 @@ struct diff_queue_struct {
 	struct diff_filepair **queue;
 	int alloc;
 	int nr;
+	int run;
 };
 #define DIFF_QUEUE_CLEAR(q) \
 	do { \
 		(q)->queue = NULL; \
 		(q)->nr = (q)->alloc = 0; \
+		(q)->run = 0; \
 	} while(0);
 
 extern struct diff_queue_struct diff_queued_diff;