diff --git a/src/blackcore/application/applicationsettings.h b/src/blackcore/application/applicationsettings.h
index e74595653..a11ad8dc0 100644
--- a/src/blackcore/application/applicationsettings.h
+++ b/src/blackcore/application/applicationsettings.h
@@ -33,7 +33,7 @@ namespace BlackCore
             static const QString &humanReadable() { static const QString name("Hotkeys"); return name; }
 
             //! \copydoc BlackMisc::TSettingTrait::isValid
-            static bool isValid(const BlackMisc::Input::CActionHotkeyList &value)
+            static bool isValid(const BlackMisc::Input::CActionHotkeyList &value, QString &)
             {
                 for (const auto &actionHotkey : value)
                 {
@@ -63,7 +63,7 @@ namespace BlackCore
             }
 
             //! \copydoc BlackMisc::TSettingTrait::isValid
-            static bool isValid(const QStringList &pluginIdentifiers)
+            static bool isValid(const QStringList &pluginIdentifiers, QString &)
             {
                 for (const QString &pluginIdentifier : pluginIdentifiers)
                 {
diff --git a/src/blackcore/vatsim/vatsimsettings.h b/src/blackcore/vatsim/vatsimsettings.h
index 4b0ed0669..3f4bfb1a3 100644
--- a/src/blackcore/vatsim/vatsimsettings.h
+++ b/src/blackcore/vatsim/vatsimsettings.h
@@ -202,7 +202,7 @@ namespace BlackCore
             static const QString &humanReadable() { static const QString name("FSD message Logging"); return name; }
 
             /* //! \copydoc BlackMisc::TSettingTrait::isValid
-            static bool isValid(const CRawFsdMessageSettings &setting)
+            static bool isValid(const CRawFsdMessageSettings &setting, QString &)
             {
                 if (setting.areRawFsdMessagesEnabled()) { return !setting.getFileDir().isEmpty(); }
                 return true;
diff --git a/src/blackgui/settings/guisettings.h b/src/blackgui/settings/guisettings.h
index 65a2db70a..f589eb076 100644
--- a/src/blackgui/settings/guisettings.h
+++ b/src/blackgui/settings/guisettings.h
@@ -92,7 +92,7 @@ namespace BlackGui
             static const QString &humanReadable() { static const QString name("Background consolidation"); return name; }
 
             //! \copydoc BlackMisc::TSettingTrait::isValid
-            static bool isValid(const int &valueInSeconds) { return valueInSeconds == -1 || (valueInSeconds >= minSecs() && valueInSeconds <= maxSecs()); }
+            static bool isValid(const int &valueInSeconds, QString &) { return valueInSeconds == -1 || (valueInSeconds >= minSecs() && valueInSeconds <= maxSecs()); }
 
             //! \copydoc BlackMisc::TSettingTrait::defaultValue
             static const int &defaultValue() { static const int i = 60; return i; }
diff --git a/src/blackgui/settings/viewupdatesettings.h b/src/blackgui/settings/viewupdatesettings.h
index c03579115..82716ae73 100644
--- a/src/blackgui/settings/viewupdatesettings.h
+++ b/src/blackgui/settings/viewupdatesettings.h
@@ -106,7 +106,7 @@ namespace BlackGui
             static const QString &humanReadable() { static const QString name("View update"); return name; }
 
             //! \copydoc BlackMisc::TSettingTrait::isValid
-            static bool isValid(const CViewUpdateSettings &settings) { return settings.isValid(); }
+            static bool isValid(const CViewUpdateSettings &settings, QString &) { return settings.isValid(); }
         };
     } // ns
 } // ns
diff --git a/src/blackmisc/audio/audiosettings.h b/src/blackmisc/audio/audiosettings.h
index 71fa0aa9c..4162144c8 100644
--- a/src/blackmisc/audio/audiosettings.h
+++ b/src/blackmisc/audio/audiosettings.h
@@ -109,7 +109,7 @@ namespace BlackMisc
             static const QString &humanReadable() { static const QString name("Audio"); return name; }
 
             //! \copydoc BlackMisc::TSettingTrait::isValid
-            static bool isValid(const BlackMisc::Audio::CSettings &value) { Q_UNUSED(value); return true; }
+            static bool isValid(const BlackMisc::Audio::CSettings &value, QString &) { Q_UNUSED(value); return true; }
         };
     } // namespace
 } // namespace
diff --git a/src/blackmisc/audio/settings/voicesettings.h b/src/blackmisc/audio/settings/voicesettings.h
index aed8d3983..e044850b0 100644
--- a/src/blackmisc/audio/settings/voicesettings.h
+++ b/src/blackmisc/audio/settings/voicesettings.h
@@ -31,7 +31,7 @@ namespace BlackMisc
                 static const QString &humanReadable() { static const QString name("Voice setup"); return name; }
 
                 //! \copydoc BlackMisc::TSettingTrait::isValid
-                static bool isValid(const CVoiceSetup &setup) { return setup.validate().isSuccess(); }
+                static bool isValid(const CVoiceSetup &setup, QString &) { return setup.validate().isSuccess(); }
             };
         } // ns
     } // ns
diff --git a/src/blackmisc/datacache.h b/src/blackmisc/datacache.h
index 8284bbb40..d11d7859d 100644
--- a/src/blackmisc/datacache.h
+++ b/src/blackmisc/datacache.h
@@ -451,7 +451,7 @@ namespace BlackMisc
 
         //! Validator function. Return true if the argument is valid, false otherwise. Default
         //! implementation just returns true. Reimplemented in derived class to support validation of the value.
-        static bool isValid(const T &) { return true; }
+        static bool isValid(const T &value, QString &reason) { Q_UNUSED(value); Q_UNUSED(reason); return true; }
 
         //! Return the value to use in case the supplied value does not satisfy the validator.
         //! Default implementation returns a default-constructed value.
diff --git a/src/blackmisc/settingscache.h b/src/blackmisc/settingscache.h
index 8909eb6ed..bb51fa649 100644
--- a/src/blackmisc/settingscache.h
+++ b/src/blackmisc/settingscache.h
@@ -144,7 +144,7 @@ namespace BlackMisc
 
         //! Validator function. Return true if the argument is valid, false otherwise. Default
         //! implementation just returns true. Reimplemented in derived class to support validation of the value.
-        static bool isValid(const T &) { return true; }
+        static bool isValid(const T &value, QString &reason) { Q_UNUSED(value); Q_UNUSED(reason); return true; }
 
         //! Return the value to use in case the supplied value does not satisfy the validator.
         //! Default implementation returns a default-constructed value.
diff --git a/src/blackmisc/simulation/modelconverterx.h b/src/blackmisc/simulation/modelconverterx.h
index 3a3e02628..a0d97f65e 100644
--- a/src/blackmisc/simulation/modelconverterx.h
+++ b/src/blackmisc/simulation/modelconverterx.h
@@ -52,7 +52,7 @@ namespace BlackMisc
                 static const char *key() { return "mapping/modelconverterxbin"; }
 
                 //! \copydoc BlackMisc::TSettingTrait::isValid
-                static bool isValid(const QString &value)
+                static bool isValid(const QString &value, QString &)
                 {
                     if (value.isEmpty()) { return true; }
                     const QFile f(value);
diff --git a/src/blackmisc/simulation/settings/fgswiftbussettings.h b/src/blackmisc/simulation/settings/fgswiftbussettings.h
index dd75c6cec..ece0c1630 100644
--- a/src/blackmisc/simulation/settings/fgswiftbussettings.h
+++ b/src/blackmisc/simulation/settings/fgswiftbussettings.h
@@ -36,8 +36,8 @@ namespace BlackMisc
                 //! \copydoc BlackMisc::TSettingTrait::defaultValue
                 static QString defaultValue() { return "tcp:host=127.0.0.1,port=45003"; }
 
-                //! \copydoc BlackMisc::TSettingTrait::defaultValue
-                static bool isValid(const QString &dBusAddress) { return BlackMisc::CDBusServer::isSessionOrSystemAddress(dBusAddress) || BlackMisc::CDBusServer::isQtDBusAddress(dBusAddress); }
+                //! \copydoc BlackMisc::TSettingTrait::isValid
+                static bool isValid(const QString &dBusAddress, QString &) { return BlackMisc::CDBusServer::isSessionOrSystemAddress(dBusAddress) || BlackMisc::CDBusServer::isQtDBusAddress(dBusAddress); }
             };
         } // ns
     } // ns
diff --git a/src/blackmisc/simulation/settings/swiftpluginsettings.h b/src/blackmisc/simulation/settings/swiftpluginsettings.h
index 7cec780ef..98537fb33 100644
--- a/src/blackmisc/simulation/settings/swiftpluginsettings.h
+++ b/src/blackmisc/simulation/settings/swiftpluginsettings.h
@@ -97,7 +97,7 @@ namespace BlackMisc
                 static const QString &humanReadable() { static const QString name("swift plugin"); return name; }
 
                 //! \copydoc BlackMisc::TSettingTrait::isValid
-                static bool isValid(const CSwiftPluginSettings &value) { return value.getEmulatedSimulator().isSingleSimulator(); }
+                static bool isValid(const CSwiftPluginSettings &value, QString &) { return value.getEmulatedSimulator().isSingleSimulator(); }
             };
         } // ns
     } // ns
diff --git a/src/blackmisc/simulation/settings/xswiftbussettings.h b/src/blackmisc/simulation/settings/xswiftbussettings.h
index 68444dfb8..0959c6347 100644
--- a/src/blackmisc/simulation/settings/xswiftbussettings.h
+++ b/src/blackmisc/simulation/settings/xswiftbussettings.h
@@ -35,8 +35,8 @@ namespace BlackMisc
                 //! \copydoc BlackMisc::TSettingTrait::defaultValue
                 static QString defaultValue() { return "tcp:host=127.0.0.1,port=45001"; }
 
-                //! \copydoc BlackMisc::TSettingTrait::defaultValue
-                static bool isValid(const QString &dBusAddress) { return BlackMisc::CDBusServer::isSessionOrSystemAddress(dBusAddress) || BlackMisc::CDBusServer::isQtDBusAddress(dBusAddress); }
+                //! \copydoc BlackMisc::TSettingTrait::isValid
+                static bool isValid(const QString &dBusAddress, QString &) { return BlackMisc::CDBusServer::isSessionOrSystemAddress(dBusAddress) || BlackMisc::CDBusServer::isQtDBusAddress(dBusAddress); }
             };
         } // ns
     } // ns
diff --git a/src/blackmisc/valuecache.cpp b/src/blackmisc/valuecache.cpp
index 3d578e8ea..7d894cf88 100644
--- a/src/blackmisc/valuecache.cpp
+++ b/src/blackmisc/valuecache.cpp
@@ -637,9 +637,11 @@ namespace BlackMisc
         key.replace("%OwnerClass%", QString(parent()->metaObject()->className()).replace("::", "/"), Qt::CaseInsensitive);
         key.replace("%OwnerName%", parent()->objectName(), Qt::CaseInsensitive);
 
+        QString unused;
         Q_ASSERT_X(! m_elements.contains(key), "CValuePage", "Can't have two CCached in the same object referring to the same value");
         Q_ASSERT_X(defaultValue.isValid() ? defaultValue.userType() == metaType : true, "CValuePage", "Metatype mismatch for default value");
-        Q_ASSERT_X(defaultValue.isValid() && validator ? validator(defaultValue) : true, "CValuePage", "Validator rejects default value");
+        Q_ASSERT_X(defaultValue.isValid() && validator ? validator(defaultValue, unused) : true, "CValuePage", "Validator rejects default value");
+        Q_UNUSED(unused);
 
         auto &element = *(m_elements[key] = ElementPtr(new Element(key, name, metaType, validator, defaultValue)));
         std::forward_as_tuple(element.m_value.uniqueWrite(), element.m_timestamp, element.m_saved) = m_cache->getValue(key);
@@ -839,6 +841,7 @@ namespace BlackMisc
 
     CStatusMessage CValuePage::validate(const Element &element, const CVariant &value, CStatusMessage::StatusSeverity invalidSeverity) const
     {
+        QString reason;
         if (! value.isValid())
         {
             return CStatusMessage(this, invalidSeverity, u"Empty cache value %1", true) << element.m_nameWithKey;
@@ -847,9 +850,16 @@ namespace BlackMisc
         {
             return CStatusMessage(this).error(u"Expected %1 but got %2 for %3") << QMetaType::typeName(element.m_metaType) << value.typeName() << element.m_nameWithKey;
         }
-        else if (element.m_validator && ! element.m_validator(value))
+        else if (element.m_validator && ! element.m_validator(value, reason))
         {
-            return CStatusMessage(this).error(u"%1 is not valid for %2") << value.toQString() << element.m_nameWithKey;
+            if (reason.isEmpty())
+            {
+                return CStatusMessage(this).error(u"%1 is not valid for %2") << value.toQString() << element.m_nameWithKey;
+            }
+            else
+            {
+                return CStatusMessage(this).error(u"%1 (%2 for %3)") << reason << value.toQString() << element.m_nameWithKey;
+            }
         }
         else
         {
diff --git a/src/blackmisc/valuecache.h b/src/blackmisc/valuecache.h
index 118bc5c6c..4891b24fe 100644
--- a/src/blackmisc/valuecache.h
+++ b/src/blackmisc/valuecache.h
@@ -444,7 +444,10 @@ namespace BlackMisc
 
     private:
         template <typename F>
-        static Private::CValuePage::Validator wrap(F func) { return [func](const CVariant &value)->bool { return func(value.to<T>()); }; }
+        static Private::CValuePage::Validator wrap(F func)
+        {
+            return [func](const CVariant &value, QString &reason) -> bool { return func(value.to<T>(), reason); };
+        }
         static Private::CValuePage::Validator wrap(std::nullptr_t) { return {}; }
 
         template <typename F>
diff --git a/src/blackmisc/valuecacheprivate.h b/src/blackmisc/valuecacheprivate.h
index b036e6df5..05e9f3000 100644
--- a/src/blackmisc/valuecacheprivate.h
+++ b/src/blackmisc/valuecacheprivate.h
@@ -72,7 +72,7 @@ namespace BlackMisc
             struct Element;
 
             //! Functor used for validating values.
-            using Validator = std::function<bool(const CVariant &)>;
+            using Validator = std::function<bool(const CVariant &, QString &)>;
 
             //! Functor used to notify parent of changes.
             using NotifySlot = std::pair<std::function<void(QObject *)>, void (QObject::*)()>;
diff --git a/tests/blackmisc/testvaluecache/testvaluecache.cpp b/tests/blackmisc/testvaluecache/testvaluecache.cpp
index 5e843650c..2f5afa509 100644
--- a/tests/blackmisc/testvaluecache/testvaluecache.cpp
+++ b/tests/blackmisc/testvaluecache/testvaluecache.cpp
@@ -314,7 +314,7 @@ namespace BlackMiscTest
     }
 
     //! Is value between 0 - 100?
-    bool validator(int value)
+    bool validator(int value, QString &)
     {
         return value >= 0 && value <= 100;
     }