diff --git a/builtin/diff-index.c b/builtin/diff-index.c
index 2eb32bd9da..1c737f7921 100644
--- a/builtin/diff-index.c
+++ b/builtin/diff-index.c
@@ -41,9 +41,13 @@ int cmd_diff_index(int argc, const char **argv, const char *prefix)
 	if (rev.pending.nr != 1 ||
 	    rev.max_count != -1 || rev.min_age != -1 || rev.max_age != -1)
 		usage(diff_cache_usage);
-	if (!cached)
+	if (!cached) {
 		setup_work_tree();
-	if (read_cache() < 0) {
+		if (read_cache_preload(rev.diffopt.pathspec.raw) < 0) {
+			perror("read_cache_preload");
+			return -1;
+		}
+	} else if (read_cache() < 0) {
 		perror("read_cache");
 		return -1;
 	}
diff --git a/builtin/diff.c b/builtin/diff.c
index 9c70e40809..8c2af6cb43 100644
--- a/builtin/diff.c
+++ b/builtin/diff.c
@@ -130,8 +130,6 @@ static int builtin_diff_index(struct rev_info *revs,
 			usage(builtin_diff_usage);
 		argv++; argc--;
 	}
-	if (!cached)
-		setup_work_tree();
 	/*
 	 * Make sure there is one revision (i.e. pending object),
 	 * and there is no revision filtering parameters.
@@ -140,8 +138,14 @@ static int builtin_diff_index(struct rev_info *revs,
 	    revs->max_count != -1 || revs->min_age != -1 ||
 	    revs->max_age != -1)
 		usage(builtin_diff_usage);
-	if (read_cache_preload(revs->diffopt.pathspec.raw) < 0) {
-		perror("read_cache_preload");
+	if (!cached) {
+		setup_work_tree();
+		if (read_cache_preload(revs->diffopt.pathspec.raw) < 0) {
+			perror("read_cache_preload");
+			return -1;
+		}
+	} else if (read_cache() < 0) {
+		perror("read_cache");
 		return -1;
 	}
 	return run_diff_index(revs, cached);
diff --git a/builtin/update-index.c b/builtin/update-index.c
index 74986bf163..ada1dff846 100644
--- a/builtin/update-index.c
+++ b/builtin/update-index.c
@@ -593,6 +593,7 @@ struct refresh_params {
 static int refresh(struct refresh_params *o, unsigned int flag)
 {
 	setup_work_tree();
+	read_cache_preload(NULL);
 	*o->has_errors |= refresh_cache(o->flags | flag);
 	return 0;
 }