diff --git a/include/polarssl/ecdsa.h b/include/polarssl/ecdsa.h
index b5e363e..4f06328 100644
--- a/include/polarssl/ecdsa.h
+++ b/include/polarssl/ecdsa.h
@@ -175,7 +175,9 @@
  * \param slen      Size of sig
  *
  * \return          0 if successful,
- *                  POLARSSL_ERR_ECP_BAD_INPUT_DATA if signature is invalid
+ *                  POLARSSL_ERR_ECP_BAD_INPUT_DATA if signature is invalid,
+ *                  POLARSSL_ERR_ECP_SIG_LEN_MISTMATCH if the signature is
+ *                  valid but its actual length is less than siglen,
  *                  or a POLARSSL_ERR_ECP or POLARSSL_ERR_MPI error code
  */
 int ecdsa_read_signature( ecdsa_context *ctx,
diff --git a/include/polarssl/ecp.h b/include/polarssl/ecp.h
index 8886048..93fbe3d 100644
--- a/include/polarssl/ecp.h
+++ b/include/polarssl/ecp.h
@@ -39,6 +39,7 @@
 #define POLARSSL_ERR_ECP_MALLOC_FAILED                     -0x4D80  /**< Memory allocation failed. */
 #define POLARSSL_ERR_ECP_RANDOM_FAILED                     -0x4D00  /**< Generation of random value, such as (ephemeral) key, failed. */
 #define POLARSSL_ERR_ECP_INVALID_KEY                       -0x4C80  /**< Invalid private or public key. */
+#define POLARSSL_ERR_ECP_SIG_LEN_MISMATCH                  -0x4C00  /**< Signature is valid but shorter than the user-supplied length. */
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/include/polarssl/error.h b/include/polarssl/error.h
index 23c0ed7..83102bd 100644
--- a/include/polarssl/error.h
+++ b/include/polarssl/error.h
@@ -87,7 +87,7 @@
  * DHM       3   9
  * PKCS5     3   4 (Started from top)
  * RSA       4   9
- * ECP       4   7 (Started from top)
+ * ECP       4   8 (Started from top)
  * MD        5   4
  * CIPHER    6   6
  * SSL       6   9 (Started from top)