diff --git a/fairmq/PluginServices.h b/fairmq/PluginServices.h
index 68d1ef33..1f0b33c4 100644
--- a/fairmq/PluginServices.h
+++ b/fairmq/PluginServices.h
@@ -178,7 +178,6 @@ class PluginServices
     auto UnsubscribeFromDeviceStateChange(const std::string& subscriber) -> void { fDevice.UnsubscribeFromStateChange(subscriber); }
 
     // Config API
-    struct PropertyNotFoundError : std::runtime_error { using std::runtime_error::runtime_error; };
 
     auto PropertyExists(const std::string& key) const -> bool { return fConfig.Count(key) > 0; }
 
@@ -200,20 +199,11 @@ class PluginServices
 
     void DeleteProperty(const std::string& key) { fConfig.DeleteProperty(key); }
 
-    /// @brief Read config property
+    /// @brief Read config property, throw if no property with this key exists
     /// @param key
     /// @return config property
-    ///
-    /// TODO Currently, if a non-existing key is requested and a default constructed object is returned.
-    /// This behaviour will be changed in the future to throw an exception in that case to provide a proper sentinel.
     template<typename T>
-    auto GetProperty(const std::string& key) const -> T
-    {
-        if (PropertyExists(key)) {
-            return fConfig.GetProperty<T>(key);
-        }
-        throw PropertyNotFoundError(fair::mq::tools::ToString("Config has no key: ", key));
-    }
+    auto GetProperty(const std::string& key) const -> T { return fConfig.GetProperty<T>(key); }
 
     template<typename T>
     T GetProperty(const std::string& key, const T& ifNotFound) const
@@ -221,18 +211,14 @@ class PluginServices
         return fConfig.GetProperty(key, ifNotFound);
     }
 
-    /// @brief Read config property as string
+    /// @brief Read config property as string, throw if no property with this key exists
     /// @param key
     /// @return config property converted to string
     ///
-    /// If a type is not supported, the user can provide support by overloading the ostream operator for this type
-    auto GetPropertyAsString(const std::string& key) const -> std::string
-    {
-        if (PropertyExists(key)) {
-            return fConfig.GetPropertyAsString(key);
-        }
-        throw PropertyNotFoundError(fair::mq::tools::ToString("Config has no key: ", key));
-    }
+    /// Supports conversion to string for a fixed set of types,
+    /// for custom/unsupported types add them via `fair::mq::PropertyHelper::AddType<MyType>("optional label")`
+    /// the provided type must then be convertible to string via operator<<
+    auto GetPropertyAsString(const std::string& key) const -> std::string { return fConfig.GetPropertyAsString(key); }
 
     auto GetPropertyAsString(const std::string& key, const std::string& ifNotFound) const -> std::string
     {
diff --git a/fairmq/ProgOptions.cxx b/fairmq/ProgOptions.cxx
index be8daabc..15ec4ce0 100644
--- a/fairmq/ProgOptions.cxx
+++ b/fairmq/ProgOptions.cxx
@@ -197,6 +197,17 @@ string ProgOptions::GetPropertyAsString(const string& key) const
 {
     lock_guard<mutex> lock(fMtx);
 
+    if (fVarMap.count(key)) {
+        return ConvertVarValToString(fVarMap.at(key));
+    } else {
+        throw PropertyNotFoundError(fair::mq::tools::ToString("Config has no key: ", key));
+    }
+}
+
+string ProgOptions::GetStringValue(const string& key) const
+{
+    lock_guard<mutex> lock(fMtx);
+
     if (fVarMap.count(key)) {
         return ConvertVarValToString(fVarMap.at(key));
     } else {
diff --git a/fairmq/ProgOptions.h b/fairmq/ProgOptions.h
index 0a59b310..8987480f 100644
--- a/fairmq/ProgOptions.h
+++ b/fairmq/ProgOptions.h
@@ -24,12 +24,15 @@
 #include <string>
 #include <unordered_map>
 #include <vector>
+#include <stdexcept>
 
 namespace fair
 {
 namespace mq
 {
 
+struct PropertyNotFoundError : std::runtime_error { using std::runtime_error::runtime_error; };
+
 class ProgOptions
 {
   public:
@@ -48,6 +51,9 @@ class ProgOptions
     std::unordered_map<std::string, int> GetChannelInfo() const;
     std::vector<std::string> GetPropertyKeys() const;
 
+    /// @brief Read config property, throw if no property with this key exists
+    /// @param key
+    /// @return config property
     template<typename T>
     T GetProperty(const std::string& key) const
     {
@@ -55,8 +61,7 @@ class ProgOptions
         if (fVarMap.count(key)) {
             return fVarMap[key].as<T>();
         } else {
-            LOG(warn) << "Config has no key: " << key << ". Returning default constructed object.";
-            return T();
+            throw PropertyNotFoundError(fair::mq::tools::ToString("Config has no key: ", key));
         }
     }
 
@@ -70,6 +75,13 @@ class ProgOptions
         return ifNotFound;
     }
 
+    /// @brief Read config property as string, throw if no property with this key exists
+    /// @param key
+    /// @return config property converted to string
+    ///
+    /// Supports conversion to string for a fixed set of types,
+    /// for custom/unsupported types add them via `fair::mq::PropertyHelper::AddType<MyType>("optional label")`
+    /// the provided type must then be convertible to string via operator<<
     std::string GetPropertyAsString(const std::string& key) const;
     std::string GetPropertyAsString(const std::string& key, const std::string& ifNotFound) const;
 
@@ -150,11 +162,26 @@ class ProgOptions
 
     const boost::program_options::variables_map& GetVarMap() const { return fVarMap; }
 
+    /// @brief Read config property, return default-constructed object if key doesn't exist
+    /// @param key
+    /// @return config property
     template<typename T>
-    T GetValue(const std::string& key) const /* TODO: deprecate this */ { return GetProperty<T>(key); }
+    T GetValue(const std::string& key) const /* TODO: deprecate this */
+    {
+        std::lock_guard<std::mutex> lock(fMtx);
+        if (fVarMap.count(key)) {
+            return fVarMap[key].as<T>();
+        } else {
+            LOG(warn) << "Config has no key: " << key << ". Returning default constructed object.";
+            return T();
+        }
+    }
     template<typename T>
     int SetValue(const std::string& key, T val) /* TODO: deprecate this */ { SetProperty(key, val); return 0; }
-    std::string GetStringValue(const std::string& key) const /* TODO: deprecate this */ { return GetPropertyAsString(key); }
+    /// @brief Read config property as string, return default-constructed object if key doesn't exist
+    /// @param key
+    /// @return config property
+    std::string GetStringValue(const std::string& key) const; /* TODO: deprecate this */
 
   private:
     void ParseDefaults();
diff --git a/test/plugin_services/_config.cxx b/test/plugin_services/_config.cxx
index b8b0ff95..c1e47b19 100644
--- a/test/plugin_services/_config.cxx
+++ b/test/plugin_services/_config.cxx
@@ -148,7 +148,7 @@ TEST_F(PluginServices, Accessors)
     // property should no longer exist after deletion
     ASSERT_EQ(mServices.PropertyExists("custom3"), false);
     // accessing this property should throw an exception
-    ASSERT_THROW(mServices.GetProperty<int>("custom3"), fair::mq::PluginServices::PropertyNotFoundError);
+    ASSERT_THROW(mServices.GetProperty<int>("custom3"), fair::mq::PropertyNotFoundError);
 
     mServices.SetProperty("customType", MyClass("message"));
     // without adding custom type information, proper string value will not be returned