diff --git a/src/modules/service_verify.c b/src/modules/service_verify.c
index 1026410..63747c7 100644
--- a/src/modules/service_verify.c
+++ b/src/modules/service_verify.c
@@ -11,6 +11,12 @@
 #define VERIFY_CONF_KEY_LOCATION    "location"
 #define VERIFY_CONF_KEY_THUMBPRINT  "esia_cert_thumbprint"
 
+#define FCGI_401_BAD_SIGNATURE_RESPONSE_FORMAT \
+        "Status: 401 Unauthorized"                      CRLF\
+        "Content-type: text/plain"                      CRLF\
+                                                        CRLF\
+        "%s"                                            CRLF
+
 static const str_t  VERIFY_CONF_DEFAULT_LOCATION    = str_t_const("/verify");
 
 static const int    CLIENT_MAX_BODY_SIZE            = 8192;
@@ -29,12 +35,14 @@ typedef struct fcgi_verify_request_s {
     char                    *content;
     int                     content_length;
 
+    char                    *verify_error;
+
 } fcgi_verify_request_t;
 
 
 static fcgi_request_handler_pt fcgi_request_finalize_handler(fcgi_handler_status_t status);
 static void fcgi_verify_request_clear(fcgi_verify_request_t *req_info);
-static fcgi_handler_status_t verify_jwt_sign(const fcgi_verify_request_t* req_info, 
+static fcgi_handler_status_t verify_jwt_sign(fcgi_verify_request_t* req_info, 
                                                 const verify_service_t *ctx);
 
 
@@ -156,7 +164,7 @@ fcgi_verify_handler(FCGX_Request* request, void* ctx)
     status = verify_jwt_sign(&req_info, ctx);
 
 exit:
-    status = fcgi_request_finalize_handler(status)(request, ctx);
+    status = fcgi_request_finalize_handler(status)(request, &req_info);
 
     fcgi_verify_request_clear(&req_info);
 
@@ -164,6 +172,27 @@ exit:
     return status;
 }
 
+static fcgi_handler_status_t 
+fcgi_401_bad_signature_handler(const FCGX_Request* request, void *ctx)
+{
+    LOG_TRACE("fcgi_401_bad_signature_handler");
+
+    const fcgi_verify_request_t *req_info = (fcgi_verify_request_t*) ctx;
+
+    assert(req_info->verify_error != NULL);
+
+    LOG_DEBUG("response status: " FCGI_401_BAD_SIGNATURE_RESPONSE_FORMAT,
+                req_info->verify_error);
+
+    if (FCGX_FPrintF(request->out, FCGI_401_BAD_SIGNATURE_RESPONSE_FORMAT, 
+                        req_info->verify_error) < 0) {
+        LOG_ERROR("FCGX_FPrintF() failed");
+        return HANDLER_ERROR;
+    }
+
+    return HANDLER_SUCCESS;
+}
+
 static fcgi_request_handler_pt
 fcgi_request_finalize_handler(fcgi_handler_status_t status)
 {
@@ -180,7 +209,7 @@ fcgi_request_finalize_handler(fcgi_handler_status_t status)
         break;
 
     case HANDLER_HTTP_UNAUTHORIZED:
-        handler = fcgi_401_unauthorized_handler;
+        handler = fcgi_401_bad_signature_handler;
         break;
 
     case HANDLER_HTTP_NOT_ACCEPTABLE:
@@ -206,6 +235,7 @@ fcgi_verify_request_clear(fcgi_verify_request_t *req_info)
     LOG_TRACE("fcgi_verify_request_clear");
 
     free(req_info->content);
+    free(req_info->verify_error);
 }
 
 static int 
@@ -276,7 +306,7 @@ error:
 }
 
 static fcgi_handler_status_t
-verify_jwt_sign(const fcgi_verify_request_t* req_info, const verify_service_t *ctx)
+verify_jwt_sign(fcgi_verify_request_t* req_info, const verify_service_t *ctx)
 {
     LOG_TRACE("verify_jwt_sign enter");
 
@@ -318,7 +348,7 @@ verify_jwt_sign(const fcgi_verify_request_t* req_info, const verify_service_t *c
     }
 
     if (cryptopro_verify(&ctx->conf->esia_cert_thumbprint, &alg, &header_payload, &sign, 
-                            &is_verified)) {
+                            &is_verified, &req_info->verify_error)) {
         goto error;
     }
 
diff --git a/src/utils/cryptopro.c b/src/utils/cryptopro.c
index 3b19603..099fbd1 100644
--- a/src/utils/cryptopro.c
+++ b/src/utils/cryptopro.c
@@ -355,28 +355,51 @@ alg_id_from_str(const str_t* alg, /*out*/ ALG_ID* alg_id)
 }
 
 static void
-log_verify_error()
+get_verify_error(char** verify_error)
 {
+    LOG_TRACE("get_verify_error enter");
+
     DWORD err = cp_function_list.GetLastError();
 
+    const char* err_string;
+
     switch (err) {
     case NTE_BAD_SIGNATURE:
-        LOG_WARN("sign is invalid: bad signature (0x%08x)", err);
+        err_string = "sign is invalid: bad signature (0x%08x)";
         break;
 
     case NTE_BAD_ALGID:
-        LOG_WARN("sign is invalid: bad alg id (0x%08x)", err);
+        err_string = "sign is invalid: bad alg id (0x%08x)";
         break;
     
     default:
-        LOG_WARN("sign is invalid. Last error code: 0x%08x", err);
+        err_string = "sign is invalid. Last error code: 0x%08x";
         break;
-    }        
+    }
+
+    size_t size = strlen(err_string) + 4 /*error code*/ + 1 /*terminating null*/;
+
+    *verify_error = malloc(size);
+    if (*verify_error == NULL) {
+        LOG_ERROR("get_verify_error failed. Could not allocate memory for error string "
+                    "(%zd bytes)", size);
+        return;
+    }
+
+    int n = snprintf(*verify_error, size, err_string, err);
+    
+    if (n < 0 || (size_t)n >= size) {
+        LOG_ERROR("get_verify_error failed. Error occurred in concatenation err_string");
+        free(*verify_error);
+        return;
+    }
+
+    LOG_TRACE("get_verify_error exit");
 }
 
 int 
-cryptopro_verify(const str_t* cert_thumbprint, const str_t* alg, const str_t *data, 
-                    const str_t *sign, bool* is_verified)
+cryptopro_verify(const str_t* cert_thumbprint, const str_t* alg, const str_t* data, 
+                    const str_t* sign, bool* is_verified, char** verify_error)
 {
     int rc = -1;
     HCERTSTORE hStoreHandle = NULL;
@@ -441,7 +464,11 @@ cryptopro_verify(const str_t* cert_thumbprint, const str_t* alg, const str_t *da
         LOG_DEBUG("sign is valid");
         *is_verified = true;
     } else {
-        log_verify_error();
+        get_verify_error(verify_error);
+        if (*verify_error == NULL) {
+            goto exit;
+        }
+        LOG_WARN("%s", *verify_error);
     }
 
     rc = 0;
diff --git a/src/utils/cryptopro.h b/src/utils/cryptopro.h
index e7efdc5..b76dbf1 100644
--- a/src/utils/cryptopro.h
+++ b/src/utils/cryptopro.h
@@ -27,6 +27,6 @@ bool cryptopro_init(const char* cp_file);
 int cryptopro_sign(const cryptopro_context_t *ctx, const str_t *data, /*out*/ str_t *sign);
 
 int cryptopro_verify(const str_t* cert_thumbprint, const str_t* alg, const str_t *data, 
-                        const str_t *sign, bool* is_verified);
+                        const str_t *sign, bool* is_verified, char** verify_error);
 
 #endif // CRYPTOPRO_H_INCLUDED