diff --git a/strbuf.c b/strbuf.c
index 88cafd4a70..b4da9f5d05 100644
--- a/strbuf.c
+++ b/strbuf.c
@@ -481,9 +481,10 @@ int strbuf_getwholeline_fd(struct strbuf *sb, int fd, int term)
 	return 0;
 }
 
-int strbuf_read_file(struct strbuf *sb, const char *path, size_t hint)
+ssize_t strbuf_read_file(struct strbuf *sb, const char *path, size_t hint)
 {
-	int fd, len;
+	int fd;
+	ssize_t len;
 
 	fd = open(path, O_RDONLY);
 	if (fd < 0)
diff --git a/strbuf.h b/strbuf.h
index 1883494ca3..1ea9d0bdeb 100644
--- a/strbuf.h
+++ b/strbuf.h
@@ -364,7 +364,7 @@ extern ssize_t strbuf_read(struct strbuf *, int fd, size_t hint);
  * Read the contents of a file, specified by its path. The third argument
  * can be used to give a hint about the file size, to avoid reallocs.
  */
-extern int strbuf_read_file(struct strbuf *sb, const char *path, size_t hint);
+extern ssize_t strbuf_read_file(struct strbuf *sb, const char *path, size_t hint);
 
 /**
  * Read the target of a symbolic link, specified by its path.  The third