diff --git a/Dockerfile b/Dockerfile
index 31d6b51..f535d91 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -19,10 +19,7 @@ ENV PYTHONDONTWRITEBYTECODE=1 \
 
 WORKDIR /app
 
-# Use HTTPS mirrors so apt works even if HTTP (port 80) is blocked in the network.
-RUN sed -i 's|http://deb.debian.org|https://deb.debian.org|g' /etc/apt/sources.list \
-    && sed -i 's|http://security.debian.org|https://security.debian.org|g' /etc/apt/sources.list \
-    && apt-get update \
+ RUN apt-get update \
     && apt-get install -y --no-install-recommends libgomp1 \
     && rm -rf /var/lib/apt/lists/*