diff --git a/upb/mini_descriptor/decode.c b/upb/mini_descriptor/decode.c
index c916f98c5a85..545f40c25434 100644
--- a/upb/mini_descriptor/decode.c
+++ b/upb/mini_descriptor/decode.c
@@ -49,15 +49,17 @@ typedef enum {
   kUpb_LayoutItemType_Max = kUpb_LayoutItemType_Field,
 } upb_LayoutItemType;
 
-#define kUpb_LayoutItem_IndexSentinel ((uint16_t) - 1)
+#define kUpb_LayoutItem_IndexSentinel ((uint16_t)-1)
 
 typedef struct {
   // Index of the corresponding field.  When this is a oneof field, the field's
   // offset will be the index of the next field in a linked list.
   uint16_t field_index;
   uint16_t offset;
-  upb_FieldRep rep;
-  upb_LayoutItemType type;
+  // These two enums are stored in bytes to avoid trailing padding while
+  // preserving two-byte alignment.
+  uint8_t /* upb_FieldRep*/ rep;
+  uint8_t /* upb_LayoutItemType*/ type;
 } upb_LayoutItem;
 
 typedef struct {