diff --git a/packages/@aws-cdk/aws-s3-deployment/lambda/build.sh b/packages/@aws-cdk/aws-s3-deployment/lambda/build.sh
index 0a33096a32672..f7997d7f7836a 100755
--- a/packages/@aws-cdk/aws-s3-deployment/lambda/build.sh
+++ b/packages/@aws-cdk/aws-s3-deployment/lambda/build.sh
@@ -27,7 +27,7 @@ cd ${staging}
 # install python requirements
 # Must use --prefix to because --target cannot be used on
 # platforms that have a default --prefix set.
-pip3 install --prefix ${piptemp} -r ${staging}/requirements.txt
+pip3 install --ignore-installed --prefix ${piptemp} -r ${staging}/requirements.txt
 mv ${piptemp}/lib/python*/site-packages/* .
 
 # create archive