diff --git a/Dockerfile b/Dockerfile
index eeb502f..78b8e42 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -33,6 +33,7 @@ RUN apt-get update && \
     libsodium-dev
 
 RUN add-apt-repository ppa:git-core/ppa && \
+    apt-get update && \
     apt-get install -y git && \
     rm -rf /var/lib/apt/lists/*