diff --git a/include/mbedtls/ecp.h b/include/mbedtls/ecp.h
index 944b7f8..f821690 100644
--- a/include/mbedtls/ecp.h
+++ b/include/mbedtls/ecp.h
@@ -36,6 +36,7 @@
 #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_IN_PROGRESS                       -0x4B80  /**< Operation in progress, try again with the same parameters. */
 
 #if !defined(MBEDTLS_ECP_ALT)
 /*