diff --git a/Dockerfile b/Dockerfile
index dcf5310..c9b49a6 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -12,7 +12,7 @@ RUN apt-get update && apt-get install -y \
     # Python
     python3 python3-dev python3-pip \
     # Camoufox build system tools
-    git p7zip-full golang-go aria2 curl \
+    git p7zip-full golang-go aria2 curl rsync \
     # CA certificates
     ca-certificates \
     && update-ca-certificates
@@ -23,10 +23,10 @@ ENV PATH="/root/.cargo/bin:${PATH}"
 # Fetch Firefox & apply initial patches
 RUN make setup-minimal && \
     make mozbootstrap && \
-    mkdir /app/dist
+    mkdir -p /app/dist
 
 # Mount .mozbuild directory and dist folder
 VOLUME /root/.mozbuild
 VOLUME /app/dist
 
-ENTRYPOINT ["python3", "./multibuild.py"]
+ENTRYPOINT ["python3", "./multibuild.py"]
\ No newline at end of file
diff --git a/additions/camoucfg/MaskConfig.hpp b/additions/camoucfg/MaskConfig.hpp
index 76fc407..28a95a7 100644
--- a/additions/camoucfg/MaskConfig.hpp
+++ b/additions/camoucfg/MaskConfig.hpp
@@ -44,7 +44,10 @@ inline std::optional<std::string> get_env_utf8(const std::string& name) {
 }
 
 inline const nlohmann::json& GetJson() {
-  static const nlohmann::json jsonConfig = []() {
+  static std::once_flag initFlag;
+  static nlohmann::json jsonConfig;
+
+  std::call_once(initFlag, []() {
     std::string jsonString;
     int index = 1;
 
@@ -63,17 +66,21 @@ inline const nlohmann::json& GetJson() {
       if (originalConfig) jsonString = *originalConfig;
     }
 
-    if (jsonString.empty()) return nlohmann::json{};
+    if (jsonString.empty()) {
+      jsonConfig = nlohmann::json{};
+      return;
+    }
 
     // Validate
     if (!nlohmann::json::accept(jsonString)) {
       printf_stderr("ERROR: Invalid JSON passed to CAMOU_CONFIG!\n");
-      return nlohmann::json{};
+      jsonConfig = nlohmann::json{};
+      return;
     }
 
-    nlohmann::json result = nlohmann::json::parse(jsonString);
-    return result;
-  }();
+    jsonConfig = nlohmann::json::parse(jsonString);
+  });
+
   return jsonConfig;
 }
 
diff --git a/multibuild.py b/multibuild.py
index 2fbdc83..e424fae 100644
--- a/multibuild.py
+++ b/multibuild.py
@@ -22,6 +22,7 @@ import os
 import sys
 from dataclasses import dataclass
 from typing import List
+import shutil
 
 # Constants
 AVAILABLE_TARGETS = ["linux", "windows", "macos"]
@@ -86,7 +87,7 @@ def run_build(target, arch):
     # Move assets to dist
     print('Assets:', ', '.join(builder.assets))
     for asset in builder.assets:
-        os.rename(asset, f'dist/{asset}')
+        shutil.move(asset, f'dist/{asset}')
 
 
 def main():