diff --git a/include/mbedtls/ecdsa.h b/include/mbedtls/ecdsa.h
index aa23d67..ff6efbc 100644
--- a/include/mbedtls/ecdsa.h
+++ b/include/mbedtls/ecdsa.h
@@ -272,8 +272,8 @@
  *
  * \return          \c 0 on success,
  *                  #MBEDTLS_ERR_ECP_BAD_INPUT_DATA if signature is invalid,
- *                  #MBEDTLS_ERR_ECP_SIG_LEN_MISMATCH if the signature is
- *                  valid but its actual length is less than \p siglen,
+ *                  #MBEDTLS_ERR_ECP_SIG_LEN_MISMATCH if there is a valid
+ *                  signature in sig but its length is less than \p siglen,
  *                  or an \c MBEDTLS_ERR_ECP_XXX or \c MBEDTLS_ERR_MPI_XXX
  *                  error code on failure for any other reason.
  *
diff --git a/include/mbedtls/ecp.h b/include/mbedtls/ecp.h
index b00ba4d..7b8ffff 100644
--- a/include/mbedtls/ecp.h
+++ b/include/mbedtls/ecp.h
@@ -36,7 +36,7 @@
 #define MBEDTLS_ERR_ECP_ALLOC_FAILED                      -0x4D80  /**< Memory allocation failed. */
 #define MBEDTLS_ERR_ECP_RANDOM_FAILED                     -0x4D00  /**< Generation of random value, such as (ephemeral) key, failed. */
 #define MBEDTLS_ERR_ECP_INVALID_KEY                       -0x4C80  /**< Invalid private or public key. */
-#define MBEDTLS_ERR_ECP_SIG_LEN_MISMATCH                  -0x4C00  /**< Signature is valid but shorter than the user-supplied length. */
+#define MBEDTLS_ERR_ECP_SIG_LEN_MISMATCH                  -0x4C00  /**< The buffer contains a valid signature followed by more data. */
 #define MBEDTLS_ERR_ECP_HW_ACCEL_FAILED                   -0x4B80  /**< ECP hardware accelerator failed. */
 
 #if !defined(MBEDTLS_ECP_ALT)
diff --git a/include/mbedtls/pk.h b/include/mbedtls/pk.h
index 1059bda..ee06b2f 100644
--- a/include/mbedtls/pk.h
+++ b/include/mbedtls/pk.h
@@ -63,7 +63,7 @@
 #define MBEDTLS_ERR_PK_INVALID_ALG         -0x3A80  /**< The algorithm tag or value is invalid. */
 #define MBEDTLS_ERR_PK_UNKNOWN_NAMED_CURVE -0x3A00  /**< Elliptic curve is unsupported (only NIST curves are supported). */
 #define MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE -0x3980  /**< Unavailable feature, e.g. RSA disabled for RSA key. */
-#define MBEDTLS_ERR_PK_SIG_LEN_MISMATCH    -0x3900  /**< The signature is valid but its length is less than expected. */
+#define MBEDTLS_ERR_PK_SIG_LEN_MISMATCH    -0x3900  /**< The buffer contains a valid signature followed by more data. */
 #define MBEDTLS_ERR_PK_HW_ACCEL_FAILED     -0x3880  /**< PK hardware accelerator failed. */
 
 #ifdef __cplusplus
@@ -269,8 +269,8 @@
  * \param sig_len   Signature length
  *
  * \return          0 on success (signature is valid),
- *                  MBEDTLS_ERR_PK_SIG_LEN_MISMATCH if the signature is
- *                  valid but its actual length is less than sig_len,
+ *                  #MBEDTLS_ERR_PK_SIG_LEN_MISMATCH if there is a valid
+ *                  signature in sig but its length is less than \p siglen,
  *                  or a specific error code.
  *
  * \note            For RSA keys, the default padding type is PKCS#1 v1.5.
@@ -300,10 +300,10 @@
  * \param sig_len   Signature length
  *
  * \return          0 on success (signature is valid),
- *                  MBEDTLS_ERR_PK_TYPE_MISMATCH if the PK context can't be
+ *                  #MBEDTLS_ERR_PK_TYPE_MISMATCH if the PK context can't be
  *                  used for this type of signatures,
- *                  MBEDTLS_ERR_PK_SIG_LEN_MISMATCH if the signature is
- *                  valid but its actual length is less than sig_len,
+ *                  #MBEDTLS_ERR_PK_SIG_LEN_MISMATCH if there is a valid
+ *                  signature in sig but its length is less than \p siglen,
  *                  or a specific error code.
  *
  * \note            If hash_len is 0, then the length associated with md_alg
diff --git a/library/ecdsa.c b/library/ecdsa.c
index 826fefe..17a88bd 100644
--- a/library/ecdsa.c
+++ b/library/ecdsa.c
@@ -400,6 +400,9 @@
                               &ctx->Q, &r, &s ) ) != 0 )
         goto cleanup;
 
+    /* At this point we know that the buffer starts with a valid signature.
+     * Return 0 if the buffer just contains the signature, and a specific
+     * error code if the valid signature is followed by more data. */
     if( p != end )
         ret = MBEDTLS_ERR_ECP_SIG_LEN_MISMATCH;
 
diff --git a/library/error.c b/library/error.c
index 0292480..b173c7e 100644
--- a/library/error.c
+++ b/library/error.c
@@ -266,7 +266,7 @@
         if( use_ret == -(MBEDTLS_ERR_ECP_INVALID_KEY) )
             mbedtls_snprintf( buf, buflen, "ECP - Invalid private or public key" );
         if( use_ret == -(MBEDTLS_ERR_ECP_SIG_LEN_MISMATCH) )
-            mbedtls_snprintf( buf, buflen, "ECP - Signature is valid but shorter than the user-supplied length" );
+            mbedtls_snprintf( buf, buflen, "ECP - The buffer contains a valid signature followed by more data" );
         if( use_ret == -(MBEDTLS_ERR_ECP_HW_ACCEL_FAILED) )
             mbedtls_snprintf( buf, buflen, "ECP - ECP hardware accelerator failed" );
 #endif /* MBEDTLS_ECP_C */
@@ -333,7 +333,7 @@
         if( use_ret == -(MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE) )
             mbedtls_snprintf( buf, buflen, "PK - Unavailable feature, e.g. RSA disabled for RSA key" );
         if( use_ret == -(MBEDTLS_ERR_PK_SIG_LEN_MISMATCH) )
-            mbedtls_snprintf( buf, buflen, "PK - The signature is valid but its length is less than expected" );
+            mbedtls_snprintf( buf, buflen, "PK - The buffer contains a valid signature followed by more data" );
         if( use_ret == -(MBEDTLS_ERR_PK_HW_ACCEL_FAILED) )
             mbedtls_snprintf( buf, buflen, "PK - PK hardware accelerator failed" );
 #endif /* MBEDTLS_PK_C */
diff --git a/library/pk_wrap.c b/library/pk_wrap.c
index a4bb35f..5446e23 100644
--- a/library/pk_wrap.c
+++ b/library/pk_wrap.c
@@ -93,6 +93,11 @@
                                   (unsigned int) hash_len, hash, sig ) ) != 0 )
         return( ret );
 
+    /* The buffer contains a valid signature followed by extra data.
+     * We have a special error code for that so that so that callers can
+     * use mbedtls_pk_verify() to check "Does the buffer start with a
+     * valid signature?" and not just "Does the buffer contain a valid
+     * signature?". */
     if( sig_len > rsa_len )
         return( MBEDTLS_ERR_PK_SIG_LEN_MISMATCH );