diff --git a/writeback.vhdl b/writeback.vhdl
index 1879a5e..042ad59 100644
--- a/writeback.vhdl
+++ b/writeback.vhdl
@@ -95,6 +95,7 @@ begin
         partial_write <= '0';
         sign_extend <= '0';
         second_word <= '0';
+        data_in <= (others => '0');
 
         if e_in.write_enable = '1' then
             w_out.write_reg <= e_in.write_reg;