diff --git a/CMakeLists.txt b/CMakeLists.txt
index e85b23f..c68151f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -30,9 +30,12 @@ set(dependencies
     esp_system
 #    esp_http_client
     esp_websocket_client
+    tcp_transport
+
     cpputils
     espchrono
-    tcp_transport
+    expected
+    fmt
 )
 
 idf_component_register(
diff --git a/src/espstrutils.cpp b/src/espstrutils.cpp
index 95c9cf5..a07e6ce 100644
--- a/src/espstrutils.cpp
+++ b/src/espstrutils.cpp
@@ -1,19 +1,29 @@
 #include "espstrutils.h"
 
-// system includes
-#include <cctype>
+// esp-idf includes
+#include <esp_log.h>
+
+// 3rdparty lib includes
+#include <fmt/core.h>
+
+// local includes
+#include "futurecpp.h"
 
 namespace espcpputils {
+namespace {
+constexpr const char * const TAG = "ESPCPPUTILS";
+}
 
 std::string toString(sntp_sync_mode_t val)
 {
     switch (val)
     {
-    case SNTP_SYNC_MODE_IMMED:  return "SNTP_SYNC_MODE_IMMED";
-    case SNTP_SYNC_MODE_SMOOTH: return "SNTP_SYNC_MODE_SMOOTH";
+    case SNTP_SYNC_MODE_IMMED:  return "IMMED";
+    case SNTP_SYNC_MODE_SMOOTH: return "SMOOTH";
+    default:
+        ESP_LOGW(TAG, "unknown sntp_sync_mode_t(%i)", std::to_underlying(val));
+        return fmt::format("Unknown sntp_sync_mode_t({})", std::to_underlying(val));
     }
-
-    return std::string{"Unknown sntp_sync_mode_t("} + std::to_string(int(val)) + ')';
 }
 
 void urldecode(char *dst, const char *src)
diff --git a/src/wrappers/websocket_client.h b/src/wrappers/websocket_client.h
index 5dcfa05..8ea4bb1 100644
--- a/src/wrappers/websocket_client.h
+++ b/src/wrappers/websocket_client.h
@@ -8,6 +8,12 @@
 #include <esp_websocket_client.h>
 #include <esp_transport_ws.h>
 
+// 3rdparty lib includes
+#include <fmt/core.h>
+
+// local includes
+#include "futurecpp.h"
+
 namespace espcpputils {
 class websocket_client
 {
@@ -56,7 +62,7 @@ public:
         case WS_TRANSPORT_OPCODES_PING:   return "PING";
         case WS_TRANSPORT_OPCODES_PONG:   return "PONG";
         case WS_TRANSPORT_OPCODES_FIN:    return "FIN";
-        default: return "unknown opcode(" + std::to_string(op_code) + ')';
+        default: return fmt::format("unknown opcode({})", std::to_underlying(op_code));
         }
     }