diff --git a/crypto/evp/evp_asn1.c b/crypto/evp/evp_asn1.c
index c57f411..da25b99 100644
--- a/crypto/evp/evp_asn1.c
+++ b/crypto/evp/evp_asn1.c
@@ -84,6 +84,9 @@
   }
 
   const uint8_t *in = *inp;
+  /* If trying to remove |old_priv_decode|, note that some code depends on this
+   * function writing into |*out| and the |priv_decode| path doesn't support
+   * that. */
   if (!ret->ameth->old_priv_decode ||
       !ret->ameth->old_priv_decode(ret, &in, len)) {
     if (ret->ameth->priv_decode) {
diff --git a/include/openssl/dh.h b/include/openssl/dh.h
index 2c49fc8..b7c07b9 100644
--- a/include/openssl/dh.h
+++ b/include/openssl/dh.h
@@ -177,7 +177,10 @@
  * structure from |len| bytes at |*inp|. If |ret| is not NULL then, on exit, a
  * pointer to the result is in |*ret|. If |*ret| is already non-NULL on entry
  * then the result is written directly into |*ret|, otherwise a fresh |DH| is
- * allocated. On successful exit, |*inp| is advanced past the DER structure. It
+ * allocated. However, one should not depend on writing into |*ret| because
+ * this behaviour is likely to change in the future.
+ *
+ * On successful exit, |*inp| is advanced past the DER structure. It
  * returns the result or NULL on error. */
 OPENSSL_EXPORT DH *d2i_DHparams(DH **ret, const unsigned char **inp, long len);
 
diff --git a/include/openssl/dsa.h b/include/openssl/dsa.h
index 2045fe7..af439bd 100644
--- a/include/openssl/dsa.h
+++ b/include/openssl/dsa.h
@@ -222,8 +222,9 @@
  * |*inp|. If |out_sig| is not NULL then, on exit, a pointer to the result is
  * in |*out_sig|. If |*out_sig| is already non-NULL on entry then the result is
  * written directly into |*out_sig|, otherwise a fresh |DSA_SIG| is allocated.
- * On successful exit, |*inp| is advanced past the DER structure. It returns
- * the result or NULL on error. */
+ * However, one should not depend on writing into |*out_sig| because this
+ * behaviour is likely to change in the future. On successful exit, |*inp| is
+ * advanced past the DER structure. It returns the result or NULL on error. */
 OPENSSL_EXPORT DSA_SIG *d2i_DSA_SIG(DSA_SIG **out_sig, const uint8_t **inp,
                                     long len);
 
@@ -236,9 +237,10 @@
 /* d2i_DSAPublicKey parses an ASN.1, DER-encoded, DSA public key from |len|
  * bytes at |*inp|. If |out| is not NULL then, on exit, a pointer to the result
  * is in |*out|. If |*out| is already non-NULL on entry then the result is
- * written directly into |*out|, otherwise a fresh |DSA| is allocated. On
- * successful exit, |*inp| is advanced past the DER structure. It returns the
- * result or NULL on error. */
+ * written directly into |*out|, otherwise a fresh |DSA| is allocated.
+ * However, one should not depend on writing into |*out| because this behaviour
+ * is likely to change in the future. On successful exit, |*inp| is advanced
+ * past the DER structure. It returns the result or NULL on error. */
 OPENSSL_EXPORT DSA *d2i_DSAPublicKey(DSA **out, const uint8_t **inp, long len);
 
 /* i2d_DSAPublicKey marshals a public key from |in| to an ASN.1, DER structure.
@@ -250,9 +252,10 @@
 /* d2i_DSAPrivateKey parses an ASN.1, DER-encoded, DSA private key from |len|
  * bytes at |*inp|. If |out| is not NULL then, on exit, a pointer to the result
  * is in |*out|. If |*out| is already non-NULL on entry then the result is
- * written directly into |*out|, otherwise a fresh |DSA| is allocated. On
- * successful exit, |*inp| is advanced past the DER structure. It returns the
- * result or NULL on error. */
+ * written directly into |*out|, otherwise a fresh |DSA| is allocated. However,
+ * one should not depend on writing into |*out| because this behaviour is
+ * likely to change in the future. On successful exit, |*inp| is advanced past
+ * the DER structure. It returns the result or NULL on error. */
 OPENSSL_EXPORT DSA *d2i_DSAPrivateKey(DSA **out, const uint8_t **inp, long len);
 
 /* i2d_DSAPrivateKey marshals a private key from |in| to an ASN.1, DER structure.
@@ -264,9 +267,10 @@
 /* d2i_DSAparams parses ASN.1, DER-encoded, DSA parameters from |len| bytes at
  * |*inp|. If |out| is not NULL then, on exit, a pointer to the result is in
  * |*out|. If |*out| is already non-NULL on entry then the result is written
- * directly into |*out|, otherwise a fresh |DSA| is allocated. On successful
- * exit, |*inp| is advanced past the DER structure. It returns the result or
- * NULL on error. */
+ * directly into |*out|, otherwise a fresh |DSA| is allocated. However, one
+ * should not depend on writing into |*out| because this behaviour is likely to
+ * change in the future. On successful exit, |*inp| is advanced past the DER
+ * structure. It returns the result or NULL on error. */
 OPENSSL_EXPORT DSA *d2i_DSAparams(DSA **out, const uint8_t **inp, long len);
 
 /* i2d_DSAparams marshals DSA parameters from |in| to an ASN.1, DER structure.
diff --git a/include/openssl/ec_key.h b/include/openssl/ec_key.h
index afd95d6..da96508 100644
--- a/include/openssl/ec_key.h
+++ b/include/openssl/ec_key.h
@@ -181,8 +181,10 @@
  * at |*inp|. If |out_key| is not NULL then, on exit, a pointer to the result
  * is in |*out_key|. If |*out_key| is already non-NULL on entry then the result
  * is written directly into |*out_key|, otherwise a fresh |EC_KEY| is
- * allocated. On successful exit, |*inp| is advanced past the DER structure. It
- * returns the result or NULL on error. */
+ * allocated. However, one should not depend on writing into |*out_key| because
+ * this behaviour is likely to change in the future. On successful exit, |*inp|
+ * is advanced past the DER structure. It returns the result or NULL on
+ * error. */
 OPENSSL_EXPORT EC_KEY *d2i_ECPrivateKey(EC_KEY **out_key, const uint8_t **inp,
                                         long len);
 
@@ -196,8 +198,10 @@
  * |len| bytes at |*inp|. If |out_key| is not NULL then, on exit, a pointer to
  * the result is in |*out_key|. If |*out_key| is already non-NULL on entry then
  * the result is written directly into |*out_key|, otherwise a fresh |EC_KEY|
- * is allocated. On successful exit, |*inp| is advanced past the DER structure.
- * It returns the result or NULL on error. */
+ * is allocated. However, one should not depend on writing into |*out_key|
+ * because this behaviour is likely to change in the future. On successful
+ * exit, |*inp| is advanced past the DER structure. It returns the result or
+ * NULL on error. */
 OPENSSL_EXPORT EC_KEY *d2i_ECParameters(EC_KEY **out_key, const uint8_t **inp,
                                         long len);
 
diff --git a/include/openssl/ecdsa.h b/include/openssl/ecdsa.h
index f3f68eb..a060eab 100644
--- a/include/openssl/ecdsa.h
+++ b/include/openssl/ecdsa.h
@@ -178,10 +178,10 @@
 
 /* d2i_ECDSA_SIG parses an ASN.1, DER-encoded, signature from |len| bytes at
  * |*inp|. If |out| is not NULL then, on exit, a pointer to the result is in
- * |*out|. If |*out| is already non-NULL on entry then the result is written
- * directly into |*out|, otherwise a fresh |ECDSA_SIG| is allocated. On
- * successful exit, |*inp| is advanced past the DER structure. It returns the
- * result or NULL on error. */
+ * |*out|. Note that, even if |*out| is already non-NULL on entry, it will not
+ * be written to. Rather, a fresh |ECDSA_SIG| is allocated and the previous one
+ * is freed. On successful exit, |*inp| is advanced past the DER structure. It
+ * returns the result or NULL on error. */
 OPENSSL_EXPORT ECDSA_SIG *d2i_ECDSA_SIG(ECDSA_SIG **out, const uint8_t **inp,
                                         long len);
 
diff --git a/include/openssl/evp.h b/include/openssl/evp.h
index be2ea33..948353a 100644
--- a/include/openssl/evp.h
+++ b/include/openssl/evp.h
@@ -192,9 +192,10 @@
 /* d2i_PrivateKey parses an ASN.1, DER-encoded, private key from |len| bytes at
  * |*inp|. If |out| is not NULL then, on exit, a pointer to the result is in
  * |*out|. If |*out| is already non-NULL on entry then the result is written
- * directly into |*out|, otherwise a fresh |EVP_PKEY| is allocated. On
- * successful exit, |*inp| is advanced past the DER structure. It returns the
- * result or NULL on error. */
+ * directly into |*out|, otherwise a fresh |EVP_PKEY| is allocated. However,
+ * one should not depend on writing into |*out| because this behaviour is
+ * likely to change in the future. On successful exit, |*inp| is advanced past
+ * the DER structure. It returns the result or NULL on error. */
 OPENSSL_EXPORT EVP_PKEY *d2i_PrivateKey(int type, EVP_PKEY **out,
                                         const uint8_t **inp, long len);
 
diff --git a/include/openssl/rsa.h b/include/openssl/rsa.h
index 304c555..62d5935 100644
--- a/include/openssl/rsa.h
+++ b/include/openssl/rsa.h
@@ -441,10 +441,10 @@
 
 /* d2i_RSAPublicKey parses an ASN.1, DER-encoded, RSA public key from |len|
  * bytes at |*inp|. If |out| is not NULL then, on exit, a pointer to the result
- * is in |*out|. If |*out| is already non-NULL on entry then the result is
- * written directly into |*out|, otherwise a fresh |RSA| is allocated. On
- * successful exit, |*inp| is advanced past the DER structure. It returns the
- * result or NULL on error. */
+ * is in |*out|. Note that, even if |*out| is already non-NULL on entry, it
+ * will not be written to. Rather, a fresh |RSA| is allocated and the previous
+ * one is freed. On successful exit, |*inp| is advanced past the DER structure.
+ * It returns the result or NULL on error. */
 OPENSSL_EXPORT RSA *d2i_RSAPublicKey(RSA **out, const uint8_t **inp, long len);
 
 /* i2d_RSAPublicKey marshals |in| to an ASN.1, DER structure. If |outp| is not
@@ -455,10 +455,10 @@
 
 /* d2i_RSAPrivateKey parses an ASN.1, DER-encoded, RSA private key from |len|
  * bytes at |*inp|. If |out| is not NULL then, on exit, a pointer to the result
- * is in |*out|. If |*out| is already non-NULL on entry then the result is
- * written directly into |*out|, otherwise a fresh |RSA| is allocated. On
- * successful exit, |*inp| is advanced past the DER structure. It returns the
- * result or NULL on error. */
+ * is in |*out|. Note that, even if |*out| is already non-NULL on entry, it
+ * will not be written to. Rather, a fresh |RSA| is allocated and the previous
+ * one is freed. On successful exit, |*inp| is advanced past the DER structure.
+ * It returns the result or NULL on error. */
 OPENSSL_EXPORT RSA *d2i_RSAPrivateKey(RSA **out, const uint8_t **inp, long len);
 
 /* i2d_RSAPrivateKey marshals |in| to an ASN.1, DER structure. If |outp| is not