diff --git a/os/hal/platforms/STM32/OTGv1/usb_lld.c b/os/hal/platforms/STM32/OTGv1/usb_lld.c
index 4af75ccd2..35b5335e5 100644
--- a/os/hal/platforms/STM32/OTGv1/usb_lld.c
+++ b/os/hal/platforms/STM32/OTGv1/usb_lld.c
@@ -246,7 +246,7 @@ static uint8_t *otg_do_push(volatile uint32_t *fifop, uint8_t *buf, size_t n) {
   while (n > 0) {
     /* Note, this line relies on the Cortex-M3/M4 ability to perform
        unaligned word accesses and on the LSB-first memory organization.*/
-    *fifop = *((uint32_t *)buf);
+    *fifop = *((PACKED_VAR uint32_t *)buf);
     buf += 4;
     n--;
   }
@@ -345,7 +345,7 @@ static uint8_t *otg_do_pop(volatile uint32_t *fifop, uint8_t *buf, size_t n) {
     uint32_t w = *fifop;
     /* Note, this line relies on the Cortex-M3/M4 ability to perform
        unaligned word accesses and on the LSB-first memory organization.*/
-    *((uint32_t *)buf) = w;
+    *((PACKED_VAR uint32_t *)buf) = w;
     buf += 4;
     n--;
   }
@@ -374,7 +374,7 @@ static void otg_fifo_read_to_buffer(volatile uint32_t *fifop,
     if (max) {
       /* Note, this line relies on the Cortex-M3/M4 ability to perform
          unaligned word accesses and on the LSB-first memory organization.*/
-      *((uint32_t *)buf) = w;
+      *((PACKED_VAR uint32_t *)buf) = w;
       buf += 4;
       max--;
     }
diff --git a/os/ports/GCC/ARMCMx/chtypes.h b/os/ports/GCC/ARMCMx/chtypes.h
index a94ae24ae..5116a79a7 100644
--- a/os/ports/GCC/ARMCMx/chtypes.h
+++ b/os/ports/GCC/ARMCMx/chtypes.h
@@ -75,6 +75,11 @@ typedef int32_t         cnt_t;          /**< Resources counter.             */
  */
 #define PACK_STRUCT_END
 
+/**
+ * @brief   Packed variable specifier.
+ */
+#define PACKED_VAR __attribute__((packed))
+
 #endif /* _CHTYPES_H_ */
 
 /** @} */
diff --git a/os/ports/IAR/ARMCMx/chtypes.h b/os/ports/IAR/ARMCMx/chtypes.h
index 9855c4e00..d2a55bbfe 100644
--- a/os/ports/IAR/ARMCMx/chtypes.h
+++ b/os/ports/IAR/ARMCMx/chtypes.h
@@ -74,6 +74,11 @@ typedef int32_t         cnt_t;          /**< Resources counter.             */
  */
 #define PACK_STRUCT_END
 
+/**
+ * @brief   Packed variable specifier.
+ */
+#define PACKED_VAR __packed
+
 #endif /* _CHTYPES_H_ */
 
 /** @} */
diff --git a/os/ports/RVCT/ARMCMx/chtypes.h b/os/ports/RVCT/ARMCMx/chtypes.h
index b3f19f674..ec76fd523 100644
--- a/os/ports/RVCT/ARMCMx/chtypes.h
+++ b/os/ports/RVCT/ARMCMx/chtypes.h
@@ -74,6 +74,11 @@ typedef int32_t         cnt_t;          /**< Resources counter.             */
  */
 #define PACK_STRUCT_END
 
+/**
+ * @brief   Packed variable specifier.
+ */
+#define PACKED_VAR __packed
+
 #endif /* _CHTYPES_H_ */
 
 /** @} */
diff --git a/readme.txt b/readme.txt
index 89dcc9460..a7045629b 100644
--- a/readme.txt
+++ b/readme.txt
@@ -100,6 +100,7 @@
 - FIX: Fixed timing issue in the STM32 OTGv1 USB driver (bug #436)(backported
   to 2.6.2).
 - FIX: Fixed STM32L1 remove reset flag (bug #435)(backported to 2.6.2).
+- FIX: Fixed unaligned data access in USB LLD (bug #434)(backported to 2.6.2).
 - FIX: Fixed add RTC to STM32L1 (bug #433)(backported to 2.6.2).
 - FIX: Fixed support 10-bit addresses in STM32 I2C driver (bug #432)
   (backported to 2.6.2).