diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 8134a7b90f0..ea5caef5a32 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -35,6 +35,7 @@ jobs:
           python tools/ci/check_line_endings.py
           python tools/ci/check_file_names.py
           python tools/ci/unticked_files.py ${GITHUB_WORKSPACE}
+          python tools/ci/illegal_dme_files.py ${GITHUB_WORKSPACE}
           python -m tools.maplint.source --github
           ~/dreamchecker > ${GITHUB_WORKSPACE}/output-annotations.txt 2>&1
       - name: Annotate Lints
diff --git a/tools/ci/illegal_dme_files.py b/tools/ci/illegal_dme_files.py
new file mode 100644
index 00000000000..bbc9ac67291
--- /dev/null
+++ b/tools/ci/illegal_dme_files.py
@@ -0,0 +1,51 @@
+# Naive search for illegal files. Has no semantic knowledge, just a lexical
+# search for specific endings in a .dme
+#
+# Illegal files are files that are allowed in the .dme by byond's standards,
+# but will cause actual issues on runtime. For example, dmm files are illegal
+# because they will mess with the map rotation system and z-levels in unexpected ways
+#
+# This is basically a slightly edited verison of unticked_files.py.
+# Look there for precise documentation on the methods used here.
+from pathlib import Path, PureWindowsPath
+import argparse
+import sys
+
+INCLUDED_FILES = [
+    'paradise.dme'
+]
+
+ILLEGAL_FILES = ( # Use a tuple here
+    '.dmm',
+)
+
+def get_illegal_files(root: Path):
+    illegal_file_count = 0
+    for includer in INCLUDED_FILES:
+        illegal_files = set()
+        with open(root / includer, 'r') as f:
+            # I've tried to optimize this, but this was the best I could get. Try placing the strips elsewhere if you dare
+            lines = [line for line in f.readlines() if line.rstrip('\r\n').strip('"').endswith(ILLEGAL_FILES)]
+            included = [line.replace('#include ', '').rstrip('\r\n').strip('"') for line in lines]
+            illegal_files.update([root / Path(includer).parent / Path(PureWindowsPath(i)) for i in included])
+
+        if len(illegal_files) >= 1:
+            illegal_file_count += len(illegal_files)
+            print(f'Found {len(illegal_files)} illegal files in {root / includer}:')
+            print('\n'.join(str(x) for x in sorted(illegal_files)), '\n')
+
+    return illegal_file_count
+
+if __name__ == '__main__':
+    parser = argparse.ArgumentParser()
+    parser.add_argument("root", help="project root directory")
+    args = parser.parse_args()
+
+    # Windows quoting behavior for directories adds trailing double-quote
+    illegal_files = get_illegal_files(Path(args.root.strip('"')))
+    if illegal_files:
+        print(f'Found {illegal_files} total illegal files.')
+        print('Illegal files are not allowed to be included in dme files.')
+        sys.exit(1)
+    else:
+        print('Found no illegal includes in main .dme.')