diff --git a/Dockerfile b/Dockerfile
index 70552c8..2c4f45a 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -5,7 +5,7 @@ ENV SQUID_CACHE_DIR=/var/spool/squid \
     SQUID_USER=proxy 
 
 WORKDIR /tmp
-RUN echo "deb http://deb.debian.org/debian buster main contrib" >> /etc/apt/sources.list && apt-get update && apt-get --no-install-recommends -y build-dep squid && apt-get install --no-install-recommends -y wget tar xz-utils libssl-dev libssl1.1 \
+RUN echo "deb-src http://deb.debian.org/debian buster main contrib" >> /etc/apt/sources.list && apt-get update && apt-get --no-install-recommends -y build-dep squid && apt-get install --no-install-recommends -y wget tar xz-utils libssl-dev libssl1.1 \
     && mkdir squid && wget http://www.squid-cache.org/Versions/v4/$SQUID_VERSION.tar.gz \
     && tar -C squid --strip-components=1 -xvf $SQUID_VERSION \
     && cd squid \