diff --git a/ARM/STMicro/STM32/drivers/stm32f4.ads b/ARM/STMicro/STM32/drivers/stm32f4.ads
index c9a5c879..e80d1184 100644
--- a/ARM/STMicro/STM32/drivers/stm32f4.ads
+++ b/ARM/STMicro/STM32/drivers/stm32f4.ads
@@ -74,9 +74,9 @@ package STM32F4 is
    type Bits_29 is mod 2**29 with Size => 29;
    type Bits_30 is mod 2**30 with Size => 30;
 
-   type Bits_32x1 is array (0 .. 31) of Bits_1 with Size => 32;
-   type Bits_16x2 is array (0 .. 15) of Bits_2 with Size => 32;
-   type Bits_8x4  is array (0 ..  7) of Bits_4 with Size => 32;
+   type Bits_32x1 is array (0 .. 31) of Bits_1 with Pack, Size => 32;
+   type Bits_16x2 is array (0 .. 15) of Bits_2 with Pack, Size => 32;
+   type Bits_8x4  is array (0 ..  7) of Bits_4 with Pack, Size => 32;
 
    --  Define address bases for the various system components