diff --git a/changelog.txt b/changelog.txt
index 550d66f7..2771987c 100644
--- a/changelog.txt
+++ b/changelog.txt
@@ -2,7 +2,6 @@
 
 change tester uid to value other than 1000 as this causes problems with WSL2 
 
-
 # 4.18.2
 
 * bugfix nginx configuration: large requests
diff --git a/nginx/nginx.conf b/nginx/nginx.conf
index d767f814..b10a4f49 100644
--- a/nginx/nginx.conf
+++ b/nginx/nginx.conf
@@ -6,7 +6,7 @@ server {
     listen 80;
 
     # increase upload size to 5 MB (default: 1MB)
-    client_max_body_size 5M;
+    client_max_body_size 50M;
 
     # server_name server.domain.org;
 
@@ -42,8 +42,8 @@ server {
 #    ssl_certificate /etc/nginx/certs/server.crt;
 #    ssl_certificate_key /etc/nginx/certs/server.key;
 
-    # increase upload size to 5 MB (default: 1MB)
-#    client_max_body_size 5M;
+    # increase upload size to 50 MB (default: 1MB)
+#    client_max_body_size 50M;
     
     # forward to django
 #    location / {
diff --git a/src/VERSION.py b/src/VERSION.py
index fc97585c..44b5bc96 100644
--- a/src/VERSION.py
+++ b/src/VERSION.py
@@ -1,3 +1,3 @@
 # -*- coding: utf-8 -*-
 
-version = "Version 4.18.3 | 20240208"
+version = "Version 4.18.3 | 20240208"
\ No newline at end of file
diff --git a/src/checker/checker/JUnitChecker.py b/src/checker/checker/JUnitChecker.py
index 2d687929..9d211dab 100644
--- a/src/checker/checker/JUnitChecker.py
+++ b/src/checker/checker/JUnitChecker.py
@@ -149,8 +149,22 @@ def remove_deprecated_warning(text):
         return text
 
     def run(self, env):
+        # Special treatment for test cases that want to analyze the original Java student code.
+        # Normally, all Java files are deleted after compilation to prevent a student from reading the test code.
+        # If there is only one file in this sandbox folder (student code), then it will be restored after deletion.
+        # This is only done if the student code consists of exactly one file,
+        # otherwise there is a risk that the student code contains test files that would overwrite the teacher's tests.
+        from pathlib import Path
+        files = list(Path(env.tmpdir()).rglob("*.[jJ][aA][vV][aA]"))
+        if len(files) == 1:
+            # create backup file
+            logger.debug(files[0])
+            import shutil
+            shutil.copyfile(str(files[0].absolute()), str(files[0].absolute()) + '__.bak')
+
         self.copy_files(env)
 
+
         # compile test
         logger.debug('JUNIT Checker build')
         java_builder = IgnoringJavaBuilder(_flags="", _libs=self.junit_version, _file_pattern=r"^.*\.[jJ][aA][vV][aA]$",
@@ -181,6 +195,11 @@ def run(self, env):
             logger.error(output)
             logger.error(error)
 
+        if len(files) == 1:
+            # restore single backup file in case of Java parser testcode
+            import shutil
+            shutil.copyfile(str(files[0].absolute()) + '__.bak', str(files[0].absolute()))
+
         # run test
         logger.debug('JUNIT Checker run')
         environ = {}