diff --git a/boot/zephyr/os.c b/boot/zephyr/os.c
index eaa60b4..4721eb1 100644
--- a/boot/zephyr/os.c
+++ b/boot/zephyr/os.c
@@ -41,7 +41,7 @@
 #define CRYPTO_HEAP_SIZE 6144
 #else
 #  if !defined(MBEDTLS_RSA_NO_CRT)
-#  define CRYPTO_HEAP_SIZE 10240
+#  define CRYPTO_HEAP_SIZE 12032
 #  else
 #  define CRYPTO_HEAP_SIZE 16384
 #  endif