diff --git a/merge-ort.c b/merge-ort.c
index fb07c8f2b3..85942cfa7c 100644
--- a/merge-ort.c
+++ b/merge-ort.c
@@ -21,6 +21,7 @@
 #include "diffcore.h"
 #include "strmap.h"
 #include "tree.h"
+#include "xdiff-interface.h"
 
 struct merge_options_internal {
 	/*
@@ -245,6 +246,9 @@ static void merge_start(struct merge_options *opt, struct merge_result *result)
 
 	assert(opt->priv == NULL);
 
+	/* Default to histogram diff.  Actually, just hardcode it...for now. */
+	opt->xdl_opts = DIFF_WITH_ALG(opt, HISTOGRAM_DIFF);
+
 	/* Initialization of opt->priv, our internal merge data */
 	opt->priv = xcalloc(1, sizeof(*opt->priv));