diff --git a/src/utils/cryptopro.c b/src/utils/cryptopro.c
index d797d4d..0ade3aa 100644
--- a/src/utils/cryptopro.c
+++ b/src/utils/cryptopro.c
@@ -76,7 +76,8 @@ cryptopro_sign(const cryptopro_context_t *ctx, const str_t *data, /*out*/ str_t
 error:
     str_t_clear(&signed_data);
     str_t_clear(&sign_reversed);
-    LOG_ERROR("cryptopro_sign exit with error");
+    LOG_ERROR("cryptopro_sign exit with error (sign_cert_thumbprint = '%.*s')", 
+                (int) ctx->cert_thumbprint->len, ctx->cert_thumbprint->data);
     return -1;
 }