diff --git a/library/error.c b/library/error.c
index db42381..5845303 100644
--- a/library/error.c
+++ b/library/error.c
@@ -225,6 +225,8 @@
             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" );
+        if( use_ret == -(MBEDTLS_ERR_ECP_IN_PROGRESS) )
+            mbedtls_snprintf( buf, buflen, "ECP - Operation in progress, try again with the same parameters" );
 #endif /* MBEDTLS_ECP_C */
 
 #if defined(MBEDTLS_MD_C)