diff --git a/boot/zephyr/include/config-ec.h b/boot/zephyr/include/config-ec.h
index 3b11295..924d633 100644
--- a/boot/zephyr/include/config-ec.h
+++ b/boot/zephyr/include/config-ec.h
@@ -65,6 +65,7 @@
 #define MBEDTLS_MD_C
 #define MBEDTLS_OID_C
 #define MBEDTLS_SHA256_C
+#define MBEDTLS_SHA256_SMALLER
 #define MBEDTLS_SHA224_C
 #define MBEDTLS_AES_C
 
diff --git a/boot/zephyr/include/config-ed25519.h b/boot/zephyr/include/config-ed25519.h
index 7e43708..95b299e 100644
--- a/boot/zephyr/include/config-ed25519.h
+++ b/boot/zephyr/include/config-ed25519.h
@@ -60,6 +60,7 @@
 #define MBEDTLS_MD_C
 #define MBEDTLS_OID_C
 #define MBEDTLS_SHA256_C
+#define MBEDTLS_SHA256_SMALLER
 #define MBEDTLS_SHA224_C
 #define MBEDTLS_SHA512_C
 #define MBEDTLS_AES_C
diff --git a/boot/zephyr/include/config-kw.h b/boot/zephyr/include/config-kw.h
index 168e56e..76d5da7 100644
--- a/boot/zephyr/include/config-kw.h
+++ b/boot/zephyr/include/config-kw.h
@@ -57,6 +57,7 @@
 #define MBEDTLS_CIPHER_MODE_CTR
 
 #define MBEDTLS_SHA256_C
+#define MBEDTLS_SHA256_SMALLER
 #define MBEDTLS_SHA224_C
 #define MBEDTLS_AES_C
 #define MBEDTLS_CIPHER_C
diff --git a/boot/zephyr/include/config-rsa-kw.h b/boot/zephyr/include/config-rsa-kw.h
index bc3da7d..b5218dd 100644
--- a/boot/zephyr/include/config-rsa-kw.h
+++ b/boot/zephyr/include/config-rsa-kw.h
@@ -63,6 +63,7 @@
 #define MBEDTLS_MD_C
 #define MBEDTLS_OID_C
 #define MBEDTLS_SHA256_C
+#define MBEDTLS_SHA256_SMALLER
 #define MBEDTLS_SHA224_C
 #define MBEDTLS_AES_C
 #define MBEDTLS_CIPHER_C
diff --git a/boot/zephyr/include/config-rsa.h b/boot/zephyr/include/config-rsa.h
index 0552420..f07c457 100644
--- a/boot/zephyr/include/config-rsa.h
+++ b/boot/zephyr/include/config-rsa.h
@@ -64,6 +64,7 @@
 #define MBEDTLS_MD_C
 #define MBEDTLS_OID_C
 #define MBEDTLS_SHA256_C
+#define MBEDTLS_SHA256_SMALLER
 #define MBEDTLS_SHA224_C
 #define MBEDTLS_AES_C