diff --git a/libfdt/fdt_sw.c b/libfdt/fdt_sw.c
index 2380b27502..55ebebf1eb 100644
--- a/libfdt/fdt_sw.c
+++ b/libfdt/fdt_sw.c
@@ -70,7 +70,7 @@ static int _fdt_sw_check_header(void *fdt)
 			return err; \
 	}
 
-static void *_fdt_grab_space(void *fdt, int len)
+static void *_fdt_grab_space(void *fdt, size_t len)
 {
 	int offset = fdt_size_dt_struct(fdt);
 	int spaceleft;