diff --git a/include/ox_aes.h b/include/ox_aes.h
index b702e368c..f09cf751d 100644
--- a/include/ox_aes.h
+++ b/include/ox_aes.h
@@ -76,8 +76,8 @@
  * @details Such container should be initialized with #cx_aes_init_key_no_throw.
  */
 struct cx_aes_key_s {
-    size_t  size;      ///< key size
-    uint8_t keys[32];  ///< key value
+    uint32_t size;      ///< key size
+    uint8_t  keys[32];  ///< key value
 };
 /** Convenience type. See #cx_aes_key_s. */
 typedef struct cx_aes_key_s cx_aes_key_t;
diff --git a/lib_cxng/include/lcx_cipher.h b/lib_cxng/include/lcx_cipher.h
index e007031e1..415ed58b2 100644
--- a/lib_cxng/include/lcx_cipher.h
+++ b/lib_cxng/include/lcx_cipher.h
@@ -42,8 +42,8 @@ typedef enum {
 
 /** Generic key structure */
 typedef struct {
-    unsigned int  size;
-    unsigned char keys[32];
+    uint32_t size;
+    uint8_t  keys[32];
 } cipher_key_t;
 
 /** Base cipher information */