diff --git a/include/mbedtls/md_internal.h b/include/mbedtls/md_internal.h
index 2cd5185..d44c8af 100644
--- a/include/mbedtls/md_internal.h
+++ b/include/mbedtls/md_internal.h
@@ -79,9 +79,21 @@
 //#define MBEDTLS_MD_INFO_SHA256
 
 /* SHA-256 */
+static inline void mbedtls_md_sha256_init_free_dummy( void* ctx )
+{
+    /* Zero-initialization can be skipped. */
+    ((void) ctx);
+}
 #define MBEDTLS_MD_INFO_SHA256_TYPE         MBEDTLS_MD_SHA256
 #define MBEDTLS_MD_INFO_SHA256_CTX_TYPE     mbedtls_sha256_context
+#if defined(MBEDTLS_MD_SINGLE_HASH)
+/* mbedtls_md_sha256_init() only zeroizes, which is redundant
+ * because mbedtls_md_context is zeroized in mbedtls_md_init(),
+ * and the mbedtls_sha256_context is embedded in mbedtls_md_context_t. */
+#define MBEDTLS_MD_INFO_SHA256_INIT_FUNC    mbedtls_md_sha256_init_free_dummy
+#else
 #define MBEDTLS_MD_INFO_SHA256_INIT_FUNC    mbedtls_sha256_init
+#endif /* MBEDTLS_MD_SINGLE_HASH */
 #define MBEDTLS_MD_INFO_SHA256_NAME         "SHA256"
 #define MBEDTLS_MD_INFO_SHA256_SIZE         32
 #define MBEDTLS_MD_INFO_SHA256_BLOCKSIZE    64
@@ -90,7 +102,14 @@
 #define MBEDTLS_MD_INFO_SHA256_FINISH_FUNC  mbedtls_sha224_finish_wrap
 #define MBEDTLS_MD_INFO_SHA256_DIGEST_FUNC  mbedtls_sha256_wrap
 #define MBEDTLS_MD_INFO_SHA256_ALLOC_FUNC   mbedtls_sha224_ctx_alloc
+#if defined(MBEDTLS_MD_SINGLE_HASH)
+/* mbedtls_md_sha256_free() only zeroizes, which is redundant
+ * because mbedtls_md_context is zeroized in mbedtls_md_init(),
+ * and the mbedtls_sha256_context is embedded in mbedtls_md_context_t. */
+#define MBEDTLS_MD_INFO_SHA256_FREE_FUNC    mbedtls_md_sha256_init_free_dummy
+#else
 #define MBEDTLS_MD_INFO_SHA256_FREE_FUNC    mbedtls_sha224_ctx_free
+#endif /* MBEDTLS_MD_SINGLE_HASH */
 #define MBEDTLS_MD_INFO_SHA256_CLONE_FUNC   mbedtls_sha224_clone_wrap
 #define MBEDTLS_MD_INFO_SHA256_PROCESS_FUNC mbedtls_sha224_process_wrap