diff --git a/include/mbedtls/dhm.h b/include/mbedtls/dhm.h
index 4d16619..caa630d 100644
--- a/include/mbedtls/dhm.h
+++ b/include/mbedtls/dhm.h
@@ -269,11 +269,12 @@
 #if defined(MBEDTLS_ASN1_PARSE_C)
 /** \ingroup x509_module */
 /**
- * \brief          Parse DHM parameters
+ * \brief          Parse DHM parameters in PEM or DER format
  *
  * \param dhm      DHM context to be initialized
  * \param dhmin    input buffer
  * \param dhminlen size of the buffer
+ *                 (including the terminating null byte for PEM data)
  *
  * \return         0 if successful, or a specific DHM or PEM error code
  */
diff --git a/include/mbedtls/pem.h b/include/mbedtls/pem.h
index ef94529..f826abd 100644
--- a/include/mbedtls/pem.h
+++ b/include/mbedtls/pem.h
@@ -73,7 +73,7 @@
  * \param ctx       context to use
  * \param header    header string to seek and expect
  * \param footer    footer string to seek and expect
- * \param data      source data to look in
+ * \param data      source data to look in (must be nul-terminated)
  * \param pwd       password for decryption (can be NULL)
  * \param pwdlen    length of password
  * \param use_len   destination for total length used (set after header is
diff --git a/include/mbedtls/pk.h b/include/mbedtls/pk.h
index 44efef0..3ed8b5e 100644
--- a/include/mbedtls/pk.h
+++ b/include/mbedtls/pk.h
@@ -427,11 +427,12 @@
 #if defined(MBEDTLS_PK_PARSE_C)
 /** \ingroup pk_module */
 /**
- * \brief           Parse a private key
+ * \brief           Parse a private key in PEM or DER format
  *
  * \param ctx       key to be initialized
  * \param key       input buffer
  * \param keylen    size of the buffer
+ *                  (including the terminating null byte for PEM data)
  * \param pwd       password for decryption (optional)
  * \param pwdlen    size of the password
  *
@@ -449,11 +450,12 @@
 
 /** \ingroup pk_module */
 /**
- * \brief           Parse a public key
+ * \brief           Parse a public key in PEM or DER format
  *
  * \param ctx       key to be initialized
  * \param key       input buffer
  * \param keylen    size of the buffer
+ *                  (including the terminating null byte for PEM data)
  *
  * \note            On entry, ctx must be empty, either freshly initialised
  *                  with mbedtls_pk_init() or reset with mbedtls_pk_free(). If you need a
diff --git a/include/mbedtls/x509_crl.h b/include/mbedtls/x509_crl.h
index 395c1b3..7b40739 100644
--- a/include/mbedtls/x509_crl.h
+++ b/include/mbedtls/x509_crl.h
@@ -101,7 +101,7 @@
  *
  * \param chain    points to the start of the chain
  * \param buf      buffer holding the CRL data in DER format
- * \param buflen   size of the buffer
+ *                 (including the terminating null byte for PEM data)
  *
  * \return         0 if successful, or a specific X509 or PEM error code
  */
@@ -115,6 +115,7 @@
  * \param chain    points to the start of the chain
  * \param buf      buffer holding the CRL data in PEM or DER format
  * \param buflen   size of the buffer
+ *                 (including the terminating null byte for PEM data)
  *
  * \return         0 if successful, or a specific X509 or PEM error code
  */
diff --git a/include/mbedtls/x509_crt.h b/include/mbedtls/x509_crt.h
index e184dee..aced7eb 100644
--- a/include/mbedtls/x509_crt.h
+++ b/include/mbedtls/x509_crt.h
@@ -141,8 +141,9 @@
  *                 correctly, the first error is returned.
  *
  * \param chain    points to the start of the chain
- * \param buf      buffer holding the certificate data
+ * \param buf      buffer holding the certificate data in PEM or DER format
  * \param buflen   size of the buffer
+ *                 (including the terminating null byte for PEM data)
  *
  * \return         0 if all certificates parsed successfully, a positive number
  *                 if partly successful or a specific X509 or PEM error code
diff --git a/include/mbedtls/x509_csr.h b/include/mbedtls/x509_csr.h
index c46bc61..0082ada 100644
--- a/include/mbedtls/x509_csr.h
+++ b/include/mbedtls/x509_csr.h
@@ -99,6 +99,7 @@
  * \param csr      CSR context to fill
  * \param buf      buffer holding the CRL data
  * \param buflen   size of the buffer
+ *                 (including the terminating null byte for PEM data)
  *
  * \return         0 if successful, or a specific X509 or PEM error code
  */