diff --git a/apps/opencs/model/doc/runner.cpp b/apps/opencs/model/doc/runner.cpp
index ccdff1444..927bda080 100644
--- a/apps/opencs/model/doc/runner.cpp
+++ b/apps/opencs/model/doc/runner.cpp
@@ -83,6 +83,8 @@ void CSMDoc::Runner::start (bool delayed)
         arguments <<
             QString::fromUtf8 (("--data=\""+mProjectPath.parent_path().string()+"\"").c_str());
 
+        arguments << "--replace=content";
+
         for (std::vector<std::string>::const_iterator iter (mContentFiles.begin());
             iter!=mContentFiles.end(); ++iter)
         {
diff --git a/apps/openmw/main.cpp b/apps/openmw/main.cpp
index 709ffda2c..8f7e16058 100644
--- a/apps/openmw/main.cpp
+++ b/apps/openmw/main.cpp
@@ -44,6 +44,10 @@ bool parseOptions (int argc, char** argv, OMW::Engine& engine, Files::Configurat
     desc.add_options()
         ("help", "print help message")
         ("version", "print version information and quit")
+
+        ("replace", bpo::value<Files::EscapeStringVector>()->default_value(Files::EscapeStringVector(), "")
+            ->multitoken()->composing(), "settings where the values from the current source should replace those from lower-priority sources instead of being appended")
+
         ("data", bpo::value<Files::EscapePathContainer>()->default_value(Files::EscapePathContainer(), "data")
             ->multitoken()->composing(), "set data directories (later directories have higher priority)")
 
@@ -192,6 +196,15 @@ bool parseOptions (int argc, char** argv, OMW::Engine& engine, Files::Configurat
         Log(Debug::Error) << "No content file given (esm/esp, nor omwgame/omwaddon). Aborting...";
         return false;
     }
+    std::set<std::string> contentDedupe;
+    for (const auto& contentFile : content)
+    {
+        if (!contentDedupe.insert(contentFile).second)
+        {
+            Log(Debug::Error) << "Content file specified more than once: " << contentFile << ". Aborting...";
+            return false;
+        }
+    }
 
     for (auto& file : content)
     {
diff --git a/components/files/configurationmanager.cpp b/components/files/configurationmanager.cpp
index 92d35a6b6..35679ef29 100644
--- a/components/files/configurationmanager.cpp
+++ b/components/files/configurationmanager.cpp
@@ -100,6 +100,17 @@ boost::program_options::variables_map ConfigurationManager::separateComposingVar
 
 void ConfigurationManager::mergeComposingVariables(boost::program_options::variables_map & first, boost::program_options::variables_map & second, boost::program_options::options_description& description)
 {
+    // There are a few places this assumes all variables are present in second, but it's never crashed in the wild, so it looks like that's guaranteed.
+    std::set<std::string> replacedVariables;
+    if (description.find_nothrow("replace", false))
+    {
+        auto replace = second["replace"];
+        if (!replace.defaulted() && !replace.empty())
+        {
+            std::vector<std::string> replaceVector = replace.as<Files::EscapeStringVector>().toStdStringVector();
+            replacedVariables.insert(replaceVector.begin(), replaceVector.end());
+        }
+    }
     for (const auto& option : description.options())
     {
         if (option->semantic()->is_composing())
@@ -113,6 +124,12 @@ void ConfigurationManager::mergeComposingVariables(boost::program_options::varia
                 continue;
             }
 
+            if (replacedVariables.count(name))
+            {
+                firstPosition->second = second[name];
+                continue;
+            }
+
             if (second[name].defaulted() || second[name].empty())
                 continue;