diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2c891d4..7b13328 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -36,7 +36,6 @@ set(dependencies
     espwifistack
     date
     espchrono
-    fmt
     nvs_flash
 )
 
diff --git a/src/configconstraints_base.h b/src/configconstraints_base.h
index eb4003d..c7236c1 100644
--- a/src/configconstraints_base.h
+++ b/src/configconstraints_base.h
@@ -3,9 +3,7 @@
 // system includes
 #include <string>
 #include <expected>
-
-// 3rdparty lib includes
-#include <fmt/core.h>
+#include <format>
 
 // local includes
 #include "configwrapper.h"
@@ -16,7 +14,7 @@ template<int MAX_LENGTH>
 ConfigConstraintReturnType StringMaxSize(const std::string &str)
 {
     if (str.size() > MAX_LENGTH)
-        return std::unexpected(fmt::format("String length  {} exceeds maximum {}", str.size(), MAX_LENGTH));
+        return std::unexpected(std::format("String length  {} exceeds maximum {}", str.size(), MAX_LENGTH));
     return {};
 }
 
@@ -24,7 +22,7 @@ template<int MIN_LENGTH, int MAX_LENGTH>
 ConfigConstraintReturnType StringMinMaxSize(const std::string &str)
 {
     if (str.size() < MIN_LENGTH || str.size() > MAX_LENGTH)
-        return std::unexpected(fmt::format("String length  {} exceeds range {} to {}", str.size(), MIN_LENGTH, MAX_LENGTH));
+        return std::unexpected(std::format("String length  {} exceeds range {} to {}", str.size(), MIN_LENGTH, MAX_LENGTH));
     return {};
 }
 
@@ -49,7 +47,7 @@ ConfigConstraintReturnType StringOr(const std::string &str)
     const auto result1 = callback1(str);
     if (result1)
         return {};
-    return std::unexpected(fmt::format("None of the following 2 constraints succeded: {} | {}", result0.error(), result1.error()));
+    return std::unexpected(std::format("None of the following 2 constraints succeded: {} | {}", result0.error(), result1.error()));
 }
 
 template<ConfigWrapper<std::string>::ConstraintCallback callback0, ConfigWrapper<std::string>::ConstraintCallback callback1, ConfigWrapper<std::string>::ConstraintCallback callback2>
@@ -64,7 +62,7 @@ ConfigConstraintReturnType StringOr(const std::string &str)
     const auto result2 = callback2(str);
     if (result2)
         return {};
-    return std::unexpected(fmt::format("None of the following 3 constraints succeded: {} | {} | {}", result0.error(), result1.error(), result2.error()));
+    return std::unexpected(std::format("None of the following 3 constraints succeded: {} | {} | {}", result0.error(), result1.error(), result2.error()));
 }
 
 template<ConfigWrapper<std::string>::ConstraintCallback callback0, ConfigWrapper<std::string>::ConstraintCallback callback1>
@@ -101,7 +99,7 @@ template<typename T, T MIN_VALUE>
 ConfigConstraintReturnType MinValue(typename ConfigWrapper<T>::value_t val)
 {
     if (val < MIN_VALUE)
-        return std::unexpected(fmt::format("Value {} exceeds minimum {}", val, MIN_VALUE));
+        return std::unexpected(std::format("Value {} exceeds minimum {}", val, MIN_VALUE));
     return {};
 }
 
@@ -109,7 +107,7 @@ template<typename T, T MAX_VALUE>
 ConfigConstraintReturnType MaxValue(typename ConfigWrapper<T>::value_t val)
 {
     if (val > MAX_VALUE)
-        return std::unexpected(fmt::format("Value {} exceeds maximum {}", val, MAX_VALUE));
+        return std::unexpected(std::format("Value {} exceeds maximum {}", val, MAX_VALUE));
     return {};
 }
 
@@ -117,7 +115,7 @@ template<typename T, T MIN_VALUE, T MAX_VALUE>
 ConfigConstraintReturnType MinMaxValue(typename ConfigWrapper<T>::value_t val)
 {
     if (val < MIN_VALUE || val > MAX_VALUE)
-        return std::unexpected(fmt::format("Value {} exceeds range {} to {}", val, MIN_VALUE, MAX_VALUE));
+        return std::unexpected(std::format("Value {} exceeds range {} to {}", val, MIN_VALUE, MAX_VALUE));
     return {};
 }
 
@@ -125,7 +123,7 @@ template<typename T>
 ConfigConstraintReturnType MinMaxValue(typename ConfigWrapper<T>::value_t val, T MIN_VALUE, T MAX_VALUE)
 {
     if (val < MIN_VALUE || val > MAX_VALUE)
-        return std::unexpected(fmt::format("Value {} exceeds range {} to {}", val, MIN_VALUE, MAX_VALUE));
+        return std::unexpected(std::format("Value {} exceeds range {} to {}", val, MIN_VALUE, MAX_VALUE));
     return {};
 }
 
@@ -133,7 +131,7 @@ template<typename T, T MIN_VALUE, T MAX_VALUE>
 ConfigConstraintReturnType MinMaxOrZeroValue(typename ConfigWrapper<T>::value_t val)
 {
     if (val != 0 && (val < MIN_VALUE || val > MAX_VALUE))
-        return std::unexpected(fmt::format("Value {} exceeds constraint 0 or range {} to {}", val, MIN_VALUE, MAX_VALUE));
+        return std::unexpected(std::format("Value {} exceeds constraint 0 or range {} to {}", val, MIN_VALUE, MAX_VALUE));
     return {};
 }
 } // namespace espconfig
diff --git a/src/configconstraints_espchrono.h b/src/configconstraints_espchrono.h
index f1a05b8..d160fa0 100644
--- a/src/configconstraints_espchrono.h
+++ b/src/configconstraints_espchrono.h
@@ -1,12 +1,8 @@
 #pragma once
 
 // system includes
-#include <string>
 #include <expected>
 
-// 3rdparty lib includes
-#include <fmt/core.h>
-
 // local includes
 #include "configwrapper.h"
 #include "espchrono.h"
diff --git a/src/configmanager_priv.h b/src/configmanager_priv.h
index 7c54e52..4cf652b 100644
--- a/src/configmanager_priv.h
+++ b/src/configmanager_priv.h
@@ -2,12 +2,15 @@
 
 #include "configmanager.h"
 
+// system includes
+#include <format>
+
 // esp-idf includes
 #include <esp_log.h>
 #include <nvs_flash.h>
 
-// local includes
-#include "espchrono.h"
+// 3rdparty lib includes
+#include <espchrono.h>
 
 #define INSTANTIATE_CONFIGMANAGER_TEMPLATES(Type) \
     namespace espconfig { \
@@ -45,7 +48,7 @@ esp_err_t ConfigManager<ConfigContainer>::init(const char *ns)
             return result;
     }
 #endif
-#else
+#else // CONFIG_NVS_ENCRYPTION
     const esp_partition_t *key_part = esp_partition_find_first(ESP_PARTITION_TYPE_DATA, ESP_PARTITION_SUBTYPE_DATA_NVS_KEYS, NULL);
     if (!key_part)
     {
@@ -87,7 +90,7 @@ esp_err_t ConfigManager<ConfigContainer>::init(const char *ns)
             return result;
     }
 #endif
-#endif
+#endif // CONFIG_NVS_ENCRYPTION
 
     {
         const auto result = nvs_open_from_partition("nvs", ns, NVS_READWRITE, &nvs_handle_user);
@@ -119,12 +122,19 @@ esp_err_t ConfigManager<ConfigContainer>::loadFromFlash()
 
     bool success = true;
     ConfigContainer::callForEveryConfig([&](ConfigWrapperInterface &config){
+        if (strlen(config.nvsName()) > 15)
+        {
+            ESP_LOGW(TAG, "config key '%s' is longer than 15 characters", config.nvsName());
+            success = false;
+            return false; // don't abort loop
+        }
+
         if (const auto result = config.loadFromFlash(nvs_handle_user); !result)
         {
             ESP_LOGE(TAG, "config parameter %s failed to load: %.*s", config.nvsName(), result.error().size(), result.error().data());
             success = false;
         }
-        return false; // dont abort the loop
+        return false; // don't abort the loop
     });
 
     const auto after = espchrono::millis_clock::now();
@@ -160,7 +170,7 @@ ConfigStatusReturnType ConfigManager<ConfigContainer>::reset()
         {
             if (!message.empty())
                 message.append(", ");
-            message.append(fmt::format("reset of {} failed: {}", config.nvsName(), result.error()));
+            message.append(std::format("reset of {} failed: {}", config.nvsName(), result.error()));
         }
         return false; // dont abort loop
     });
diff --git a/src/configwrapper.h b/src/configwrapper.h
index 3bf8630..a37b815 100644
--- a/src/configwrapper.h
+++ b/src/configwrapper.h
@@ -39,7 +39,17 @@ public:
 
     virtual ConfigConstraintReturnType checkValue(value_t value) const = 0;
 
-    const T &value() const { return m_value; }
+    const T &value() const
+    {
+#if defined(CONFIG_COMPILER_CXX_EXCEPTIONS) && CONFIG_COMPILER_CXX_EXCEPTIONS != 0
+        if (!m_loaded)
+            throw std::runtime_error("ConfigWrapper::value() called without loading first");
+#else
+#warning "COMPILER_CXX_EXCEPTIONS disabled, ConfigWrapper::value() called without loading first will assert"
+        assert(m_loaded);
+#endif
+        return m_value;
+    }
 
 private:
     ConfigStatusReturnType writeToFlash(nvs_handle_t nvsHandle, value_t value);
diff --git a/src/configwrapper_priv.h b/src/configwrapper_priv.h
index 93609bc..224de75 100644
--- a/src/configwrapper_priv.h
+++ b/src/configwrapper_priv.h
@@ -9,13 +9,11 @@
 // system includes
 #include <utility>
 #include <cassert>
+#include <format>
 
 // esp-idf includes
 #include <esp_log.h>
 
-// 3rdparty lib includes
-#include <fmt/core.h>
-
 // local includes
 #include "configwrapper.h"
 #include "cpputils.h"