diff --git a/src/diff_tform.c b/src/diff_tform.c
index ae0fd36d6..66a4702f2 100644
--- a/src/diff_tform.c
+++ b/src/diff_tform.c
@@ -170,21 +170,21 @@ int git_diff_merge(
 	return error;
 }
 
-#define FIND_SIMILAR_HASHSIG(NAME,OPT) \
-	static int find_similar__hashsig_for_file ## NAME( \
-		void **out, const git_diff_file *f, const char *path, void *p) { \
-		GIT_UNUSED(f); GIT_UNUSED(p); \
-		return git_hashsig_create_fromfile((git_hashsig **)out, path, OPT); \
-	} \
-	static int find_similar__hashsig_for_buf ## NAME( \
-		void **out, const git_diff_file *f, const char *buf, size_t len, void *p) { \
-		GIT_UNUSED(f); GIT_UNUSED(p); \
-		return git_hashsig_create((git_hashsig **)out, buf, len, OPT); \
-	}
+static int find_similar__hashsig_for_file(
+	void **out, const git_diff_file *f, const char *path, void *p)
+{
+	git_hashsig_option_t opt = (git_hashsig_option_t)p;
+	GIT_UNUSED(f);
+	return git_hashsig_create_fromfile((git_hashsig **)out, path, opt);
+}
 
-FIND_SIMILAR_HASHSIG(_default, GIT_HASHSIG_SMART_WHITESPACE);
-FIND_SIMILAR_HASHSIG(_ignore_whitespace, GIT_HASHSIG_IGNORE_WHITESPACE);
-FIND_SIMILAR_HASHSIG(_include_whitespace, GIT_HASHSIG_NORMAL);
+static int find_similar__hashsig_for_buf(
+	void **out, const git_diff_file *f, const char *buf, size_t len, void *p)
+{
+	git_hashsig_option_t opt = (git_hashsig_option_t)p;
+	GIT_UNUSED(f);
+	return git_hashsig_create((git_hashsig **)out, buf, len, opt);
+}
 
 static void find_similar__hashsig_free(void *sig, void *payload)
 {
@@ -200,30 +200,6 @@ static int find_similar__calc_similarity(
 	return 0;
 }
 
-static git_diff_similarity_metric find_similar__internal_metrics[3] = {
-	{
-		find_similar__hashsig_for_file_default,
-		find_similar__hashsig_for_buf_default,
-		find_similar__hashsig_free,
-		find_similar__calc_similarity,
-		NULL
-	},
-	{
-		find_similar__hashsig_for_file_ignore_whitespace,
-		find_similar__hashsig_for_buf_ignore_whitespace,
-		find_similar__hashsig_free,
-		find_similar__calc_similarity,
-		NULL
-	},
-	{
-		find_similar__hashsig_for_file_include_whitespace,
-		find_similar__hashsig_for_buf_include_whitespace,
-		find_similar__hashsig_free,
-		find_similar__calc_similarity,
-		NULL
-	}
-};
-
 #define DEFAULT_THRESHOLD 50
 #define DEFAULT_BREAK_REWRITE_THRESHOLD 60
 #define DEFAULT_TARGET_LIMIT 200
@@ -292,14 +268,22 @@ static int normalize_find_opts(
 			opts->target_limit = limit;
 	}
 
-	/* for now, always assign the same internal metric */
+	/* assign the internal metric with whitespace flag as payload */
 	if (!opts->metric) {
+		opts->metric = git__malloc(sizeof(git_diff_similarity_metric));
+		GITERR_CHECK_ALLOC(opts->metric);
+
+		opts->metric->file_signature = find_similar__hashsig_for_file;
+		opts->metric->buffer_signature = find_similar__hashsig_for_buf;
+		opts->metric->free_signature = find_similar__hashsig_free;
+		opts->metric->similarity = find_similar__calc_similarity;
+
 		if (opts->flags & GIT_DIFF_FIND_IGNORE_WHITESPACE)
-			opts->metric = &find_similar__internal_metrics[1];
+			opts->metric->payload = (void *)GIT_HASHSIG_IGNORE_WHITESPACE;
 		else if (opts->flags & GIT_DIFF_FIND_DONT_IGNORE_WHITESPACE)
-			opts->metric = &find_similar__internal_metrics[2];
+			opts->metric->payload = (void *)GIT_HASHSIG_NORMAL;
 		else
-			opts->metric = &find_similar__internal_metrics[0];
+			opts->metric->payload = (void *)GIT_HASHSIG_SMART_WHITESPACE;
 	}
 
 	return 0;
@@ -667,6 +651,9 @@ cleanup:
 	}
 	git__free(cache);
 
+	if (!given_opts || !given_opts->metric)
+		git__free(opts.metric);
+
 	return error;
 }