diff --git a/include/mbedtls/cipher.h b/include/mbedtls/cipher.h
index 591aa79..1ae847d 100644
--- a/include/mbedtls/cipher.h
+++ b/include/mbedtls/cipher.h
@@ -193,7 +193,7 @@
 /** Maximum length of any IV, in Bytes. */
 #define MBEDTLS_MAX_IV_LENGTH      16
 /** Maximum block size of any cipher, in Bytes. */
-#define MBEDTLS_MAX_BLOCK_LENGTH   64
+#define MBEDTLS_MAX_BLOCK_LENGTH   16
 
 /**
  * Base cipher information (opaque struct).