diff --git a/src/rag_engine.py b/src/rag_engine.py
index 350b0130..f90523e7 100644
--- a/src/rag_engine.py
+++ b/src/rag_engine.py
@@ -204,6 +204,10 @@ class RAGEngine:
    db_path = os.path.abspath(os.path.join(self.base_dir, ".slop_cache", f"chroma_{self.collection.name}"))
    if os.path.exists(db_path):
     shutil.rmtree(db_path, ignore_errors=True)
+   chroma_module = _get_chromadb()
+   if chroma_module is None:
+    return Result(data=None, errors=[ErrorInfo(kind=ErrorKind.CONFIG, message="chromadb is not installed", source="rag._validate_collection_dim")])
+   chromadb, _ = chroma_module
    self.client = chromadb.PersistentClient(path=os.path.dirname(db_path))
    self.collection = self.client.get_or_create_collection(name=self.collection.name)
    return Result(data=None)