diff --git a/Dockerfile b/Dockerfile
index 06df1a5..67fe0ef 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -4,6 +4,10 @@ WORKDIR /build
 
 COPY pyproject.toml .
 
+# Add Zscaler public cert, see https://github.com/cfpb/zscaler-cert.
+ADD https://raw.githubusercontent.com/cfpb/zscaler-cert/3982ebd9edf9de9267df8d1732ff5a6f88e38375/zscaler_root_ca.pem /usr/local/share/ca-certificates/zscaler_root_ca.crt
+RUN update-ca-certificates
+
 RUN apk update --no-cache && apk upgrade --no-cache && \
     pip install --no-cache-dir --prefix=/install .
 
@@ -19,6 +23,10 @@ COPY --from=builder /install /usr/local
 WORKDIR /app
 COPY app.py .
 
+# Add Zscaler public cert, see https://github.com/cfpb/zscaler-cert.
+ADD https://raw.githubusercontent.com/cfpb/zscaler-cert/3982ebd9edf9de9267df8d1732ff5a6f88e38375/zscaler_root_ca.pem /usr/local/share/ca-certificates/zscaler_root_ca.crt
+RUN update-ca-certificates
+
 RUN apk update --no-cache && apk upgrade --no-cache
 
 USER appuser