diff --git a/components/esp32/include/soc/i2c_struct.h b/components/esp32/include/soc/i2c_struct.h
index 26b7f4c786..a29a9c5286 100644
--- a/components/esp32/include/soc/i2c_struct.h
+++ b/components/esp32/include/soc/i2c_struct.h
@@ -97,8 +97,8 @@ typedef volatile struct {
     } fifo_conf;
     union {
         struct {
-            uint32_t data:       8;                 /*The register represent the byte  data read from rx_fifo when use apb fifo access*/
-            uint32_t reserved8: 24;
+            uint8_t data;                           /*The register represent the byte  data read from rx_fifo when use apb fifo access*/
+            uint8_t reserved[3];
         };
         uint32_t val;
     } fifo_data;
diff --git a/components/esp32/include/soc/uart_struct.h b/components/esp32/include/soc/uart_struct.h
index 115ada40f9..05b54867be 100644
--- a/components/esp32/include/soc/uart_struct.h
+++ b/components/esp32/include/soc/uart_struct.h
@@ -16,8 +16,8 @@
 typedef volatile struct {
     union {
         struct {
-            uint32_t rw_byte:    8;                 /*This register stores one byte data  read by rx fifo.*/
-            uint32_t reserved8: 24;
+            uint8_t rw_byte;                 /*This register stores one byte data  read by rx fifo.*/
+            uint8_t reserved[3];
         };
         uint32_t val;
     } fifo;