diff --git a/hash.c b/hash.c
index 63672a3d22..55d1d41770 100644
--- a/hash.c
+++ b/hash.c
@@ -72,6 +72,11 @@ static void git_hash_sha1_final_oid(struct object_id *oid, struct git_hash_ctx *
 	oid->algo = GIT_HASH_SHA1;
 }
 
+static void git_hash_sha1_discard(struct git_hash_ctx *ctx)
+{
+	git_SHA1_Discard(&ctx->state.sha1);
+}
+
 static void git_hash_sha1_init_unsafe(struct git_hash_ctx *ctx)
 {
 	ctx->algop = unsafe_hash_algo(&hash_algos[GIT_HASH_SHA1]);
@@ -102,6 +107,11 @@ static void git_hash_sha1_final_oid_unsafe(struct object_id *oid, struct git_has
 	oid->algo = GIT_HASH_SHA1;
 }
 
+static void git_hash_sha1_discard_unsafe(struct git_hash_ctx *ctx)
+{
+	git_SHA1_Discard_unsafe(&ctx->state.sha1_unsafe);
+}
+
 static void git_hash_sha256_init(struct git_hash_ctx *ctx)
 {
 	ctx->algop = unsafe_hash_algo(&hash_algos[GIT_HASH_SHA256]);
@@ -135,6 +145,11 @@ static void git_hash_sha256_final_oid(struct object_id *oid, struct git_hash_ctx
 	oid->algo = GIT_HASH_SHA256;
 }
 
+static void git_hash_sha256_discard(struct git_hash_ctx *ctx)
+{
+	git_SHA256_Discard(&ctx->state.sha256);
+}
+
 static void git_hash_unknown_init(struct git_hash_ctx *ctx UNUSED)
 {
 	BUG("trying to init unknown hash");
@@ -165,6 +180,11 @@ static void git_hash_unknown_final_oid(struct object_id *oid UNUSED,
 	BUG("trying to finalize unknown hash");
 }
 
+static void git_hash_unknown_discard(struct git_hash_ctx *ctx UNUSED)
+{
+	BUG("trying to discard unknown hash");
+}
+
 static const struct git_hash_algo sha1_unsafe_algo = {
 	.name = "sha1",
 	.format_id = GIT_SHA1_FORMAT_ID,
@@ -176,6 +196,7 @@ static const struct git_hash_algo sha1_unsafe_algo = {
 	.update_fn = git_hash_sha1_update_unsafe,
 	.final_fn = git_hash_sha1_final_unsafe,
 	.final_oid_fn = git_hash_sha1_final_oid_unsafe,
+	.discard_fn = git_hash_sha1_discard_unsafe,
 	.empty_tree = &empty_tree_oid,
 	.empty_blob = &empty_blob_oid,
 	.null_oid = &null_oid_sha1,
@@ -193,6 +214,7 @@ const struct git_hash_algo hash_algos[GIT_HASH_NALGOS] = {
 		.update_fn = git_hash_unknown_update,
 		.final_fn = git_hash_unknown_final,
 		.final_oid_fn = git_hash_unknown_final_oid,
+		.discard_fn = git_hash_unknown_discard,
 		.empty_tree = NULL,
 		.empty_blob = NULL,
 		.null_oid = NULL,
@@ -208,6 +230,7 @@ const struct git_hash_algo hash_algos[GIT_HASH_NALGOS] = {
 		.update_fn = git_hash_sha1_update,
 		.final_fn = git_hash_sha1_final,
 		.final_oid_fn = git_hash_sha1_final_oid,
+		.discard_fn = git_hash_sha1_discard,
 		.unsafe = &sha1_unsafe_algo,
 		.empty_tree = &empty_tree_oid,
 		.empty_blob = &empty_blob_oid,
@@ -224,6 +247,7 @@ const struct git_hash_algo hash_algos[GIT_HASH_NALGOS] = {
 		.update_fn = git_hash_sha256_update,
 		.final_fn = git_hash_sha256_final,
 		.final_oid_fn = git_hash_sha256_final_oid,
+		.discard_fn = git_hash_sha256_discard,
 		.empty_tree = &empty_tree_oid_sha256,
 		.empty_blob = &empty_blob_oid_sha256,
 		.null_oid = &null_oid_sha256,
@@ -285,14 +309,7 @@ void git_hash_final_oid(struct object_id *oid, struct git_hash_ctx *ctx)
 
 void git_hash_discard(struct git_hash_ctx *ctx)
 {
-	/*
-	 * XXX Many implementations do not need to do anything here,
-	 * and a dummy final() call is wasteful. But we can't fix
-	 * that unless our implementation API exposes a discard
-	 * primitive.
-	 */
-	unsigned char dummy[GIT_MAX_RAWSZ];
-	git_hash_final(dummy, ctx);
+	ctx->algop->discard_fn(ctx);
 }
 
 uint32_t hash_algo_by_name(const char *name)
diff --git a/hash.h b/hash.h
index 6b2f04e2a4..0a23ef4dfd 100644
--- a/hash.h
+++ b/hash.h
@@ -37,6 +37,7 @@
 #    define platform_SHA1_Clone_unsafe openssl_SHA1_Clone
 #    define platform_SHA1_Update_unsafe openssl_SHA1_Update
 #    define platform_SHA1_Final_unsafe openssl_SHA1_Final
+#    define platform_SHA1_Discard_unsafe openssl_SHA1_Discard
 #  else
 #    define platform_SHA_CTX_unsafe SHA_CTX
 #    define platform_SHA1_Init_unsafe SHA1_Init
@@ -92,6 +93,7 @@
 #  define platform_SHA1_Final_unsafe   platform_SHA1_Final
 #  ifdef platform_SHA1_Clone
 #    define platform_SHA1_Clone_unsafe platform_SHA1_Clone
+#    define platform_SHA1_Discard_unsafe platform_SHA1_Discard
 #  endif
 #  ifdef SHA1_NEEDS_CLONE_HELPER
 #    define SHA1_NEEDS_CLONE_HELPER_UNSAFE
@@ -110,9 +112,11 @@
 
 #ifdef platform_SHA1_Clone
 #define git_SHA1_Clone	platform_SHA1_Clone
+#define git_SHA1_Discard platform_SHA1_Discard
 #endif
 #ifdef platform_SHA1_Clone_unsafe
 #  define git_SHA1_Clone_unsafe platform_SHA1_Clone_unsafe
+#  define git_SHA1_Discard_unsafe platform_SHA1_Discard_unsafe
 #endif
 
 #ifndef platform_SHA256_CTX
@@ -129,6 +133,7 @@
 
 #ifdef platform_SHA256_Clone
 #define git_SHA256_Clone	platform_SHA256_Clone
+#define git_SHA256_Discard	platform_SHA256_Discard
 #endif
 
 #ifdef SHA1_MAX_BLOCK_SIZE
@@ -142,6 +147,10 @@ static inline void git_SHA1_Clone(git_SHA_CTX *dst, const git_SHA_CTX *src)
 {
 	memcpy(dst, src, sizeof(*dst));
 }
+static inline void git_SHA1_Discard(git_SHA_CTX *ctx UNUSED)
+{
+	/* noop */
+}
 #endif
 #ifndef SHA1_NEEDS_CLONE_HELPER_UNSAFE
 static inline void git_SHA1_Clone_unsafe(git_SHA_CTX_unsafe *dst,
@@ -149,6 +158,10 @@ static inline void git_SHA1_Clone_unsafe(git_SHA_CTX_unsafe *dst,
 {
 	memcpy(dst, src, sizeof(*dst));
 }
+static inline void git_SHA1_Discard_unsafe(git_SHA_CTX_unsafe *ctx UNUSED)
+{
+	/* noop */
+}
 #endif
 
 #ifndef SHA256_NEEDS_CLONE_HELPER
@@ -156,6 +169,10 @@ static inline void git_SHA256_Clone(git_SHA256_CTX *dst, const git_SHA256_CTX *s
 {
 	memcpy(dst, src, sizeof(*dst));
 }
+static inline void git_SHA256_Discard(git_SHA256_CTX *ctx UNUSED)
+{
+	/* noop */
+}
 #endif
 
 /*
@@ -271,6 +288,7 @@ typedef void (*git_hash_clone_fn)(struct git_hash_ctx *dst, const struct git_has
 typedef void (*git_hash_update_fn)(struct git_hash_ctx *ctx, const void *in, size_t len);
 typedef void (*git_hash_final_fn)(unsigned char *hash, struct git_hash_ctx *ctx);
 typedef void (*git_hash_final_oid_fn)(struct object_id *oid, struct git_hash_ctx *ctx);
+typedef void (*git_hash_discard_fn)(struct git_hash_ctx *ctx);
 
 struct git_hash_algo {
 	/*
@@ -306,6 +324,9 @@ struct git_hash_algo {
 	/* The hash finalization function for object IDs. */
 	git_hash_final_oid_fn final_oid_fn;
 
+	/* Discard an initialized hash without finalizing. */
+	git_hash_discard_fn discard_fn;
+
 	/* The OID of the empty tree. */
 	const struct object_id *empty_tree;
 
diff --git a/sha1/openssl.h b/sha1/openssl.h
index 1038af47da..48deeb724a 100644
--- a/sha1/openssl.h
+++ b/sha1/openssl.h
@@ -40,12 +40,18 @@ static inline void openssl_SHA1_Clone(struct openssl_SHA1_CTX *dst,
 	EVP_MD_CTX_copy_ex(dst->ectx, src->ectx);
 }
 
+static inline void openssl_SHA1_Discard(struct openssl_SHA1_CTX *ctx)
+{
+	EVP_MD_CTX_free(ctx->ectx);
+}
+
 #ifndef platform_SHA_CTX
 #define platform_SHA_CTX openssl_SHA1_CTX
 #define platform_SHA1_Init openssl_SHA1_Init
 #define platform_SHA1_Clone openssl_SHA1_Clone
 #define platform_SHA1_Update openssl_SHA1_Update
 #define platform_SHA1_Final openssl_SHA1_Final
+#define platform_SHA1_Discard openssl_SHA1_Discard
 #endif
 
 #endif /* SHA1_OPENSSL_H */
diff --git a/sha256/gcrypt.h b/sha256/gcrypt.h
index 694a2b70a1..d91ffe73d3 100644
--- a/sha256/gcrypt.h
+++ b/sha256/gcrypt.h
@@ -31,10 +31,16 @@ static inline void gcrypt_SHA256_Clone(gcrypt_SHA256_CTX *dst, const gcrypt_SHA2
 	gcry_md_copy(dst, *src);
 }
 
+static inline void gcrypt_SHA256_Discard(gcrypt_SHA256_CTX *ctx)
+{
+	gcry_md_close(*ctx);
+}
+
 #define platform_SHA256_CTX gcrypt_SHA256_CTX
 #define platform_SHA256_Init gcrypt_SHA256_Init
 #define platform_SHA256_Clone gcrypt_SHA256_Clone
 #define platform_SHA256_Update gcrypt_SHA256_Update
 #define platform_SHA256_Final gcrypt_SHA256_Final
+#define platform_SHA256_Discard gcrypt_SHA256_Discard
 
 #endif
diff --git a/sha256/openssl.h b/sha256/openssl.h
index c1083d9491..3d457ca99d 100644
--- a/sha256/openssl.h
+++ b/sha256/openssl.h
@@ -40,10 +40,16 @@ static inline void openssl_SHA256_Clone(struct openssl_SHA256_CTX *dst,
 	EVP_MD_CTX_copy_ex(dst->ectx, src->ectx);
 }
 
+static inline void openssl_SHA256_Discard(struct openssl_SHA256_CTX *ctx)
+{
+	EVP_MD_CTX_free(ctx->ectx);
+}
+
 #define platform_SHA256_CTX openssl_SHA256_CTX
 #define platform_SHA256_Init openssl_SHA256_Init
 #define platform_SHA256_Clone openssl_SHA256_Clone
 #define platform_SHA256_Update openssl_SHA256_Update
 #define platform_SHA256_Final openssl_SHA256_Final
+#define platform_SHA256_Discard openssl_SHA256_Discard
 
 #endif /* SHA256_OPENSSL_H */