diff --git a/13/Dockerfile b/13/Dockerfile
index b5ba4f2750..5af43256f4 100644
--- a/13/Dockerfile
+++ b/13/Dockerfile
@@ -118,6 +118,8 @@ RUN set -ex; \
 			\
 # build .deb files from upstream's source packages (which are verified by apt-get)
 			apt-get update; \
+# we need DEBIAN_FRONTEND on postgresql-13 for slapd ("Please enter the password for the admin entry in your LDAP directory."); see https://bugs.debian.org/929417
+			DEBIAN_FRONTEND=noninteractive \
 			apt-get build-dep -y \
 				postgresql-common pgdg-keyring \
 				"postgresql-$PG_MAJOR=$PG_VERSION" \
diff --git a/Dockerfile-debian.template b/Dockerfile-debian.template
index 407b392cd5..641afc8f5e 100644
--- a/Dockerfile-debian.template
+++ b/Dockerfile-debian.template
@@ -118,6 +118,8 @@ RUN set -ex; \
 			\
 # build .deb files from upstream's source packages (which are verified by apt-get)
 			apt-get update; \
+# we need DEBIAN_FRONTEND on postgresql-13 for slapd ("Please enter the password for the admin entry in your LDAP directory."); see https://bugs.debian.org/929417
+			DEBIAN_FRONTEND=noninteractive \
 			apt-get build-dep -y \
 				postgresql-common pgdg-keyring \
 				"postgresql-$PG_MAJOR=$PG_VERSION" \
diff --git a/update.sh b/update.sh
index 4384e0ec97..2e76a6891c 100755
--- a/update.sh
+++ b/update.sh
@@ -125,6 +125,10 @@ for version in "${versions[@]}"; do
 		sed -i -e '/postgresql-contrib-/d' "$version/Dockerfile"
 	fi
 
+	if [ "$majorVersion" != '13' ]; then
+		sed -i -e '/DEBIAN_FRONTEND/d' "$version/Dockerfile"
+	fi
+
 	# TODO figure out what to do with odd version numbers here, like release candidates
 	srcVersion="${fullVersion%%-*}"
 	# change "10~beta1" to "10beta1" for ftp urls