diff --git a/Dockerfile b/Dockerfile
index 8b5a9ec8f..1a73e6080 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -22,11 +22,11 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
 		pkg-config \
                 libsqlite3-dev
 
-ENV GOLANG_VERSION 1.13.1
+ENV GOLANG_VERSION 1.13.5
 
 WORKDIR /usr/local
 RUN wget -O go.tgz https://dl.google.com/go/go${GOLANG_VERSION}.linux-amd64.tar.gz
-RUN echo "94f874037b82ea5353f4061e543681a0e79657f787437974214629af8407d124 go.tgz" | sha256sum -c -
+RUN echo "512103d7ad296467814a6e3f635631bd35574cab3369a97a323c9a585ccaa569 go.tgz" | sha256sum -c -
 RUN tar -zxvf go.tgz
 
 ENV GOROOT /usr/local/go
diff --git a/make.go b/make.go
index 008fa9fd9..3e304ce54 100644
--- a/make.go
+++ b/make.go
@@ -65,6 +65,7 @@ var (
 	camnetdns      = flag.Bool("camnetdns", false, "Just build perkeep.org/server/camnetdns.")
 	static         = flag.Bool("static", false, "Build a static binary, so it can run in an empty container.")
 	buildWebUI     = flag.Bool("buildWebUI", false, "Rebuild the JS code of the web UI instead of fetching it from perkeep.org.")
+	offline        = flag.Bool("offline", false, "Do not fetch the JS code for the web UI from perkeep.org. If not rebuilding the web UI, just trust the files on disk (if they exist).")
 )
 
 var (
@@ -594,7 +595,28 @@ func doUI(withPerkeepd, withPublisher bool) error {
 	}
 
 	if !*buildWebUI {
-		return fetchAllJS(withPerkeepd, withPublisher)
+		if !*offline {
+			return fetchAllJS(withPerkeepd, withPublisher)
+		}
+		if withPublisher {
+			_, err := os.Stat(filepath.FromSlash(publisherJS))
+			if os.IsNotExist(err) {
+				return fmt.Errorf("%s on disk is required for offline building. Fetch if first at %s.", publisherJS, publisherJSURL)
+			}
+			if err != nil {
+				return err
+			}
+		}
+		if withPerkeepd {
+			_, err := os.Stat(filepath.FromSlash(gopherjsUI))
+			if os.IsNotExist(err) {
+				return fmt.Errorf("%s on disk is required for offline building. Fetch if first at %s.", gopherjsUI, gopherjsUIURL)
+			}
+			if err != nil {
+				return err
+			}
+		}
+		return nil
 	}
 
 	if os.Getenv("GO111MODULE") != "off" {
diff --git a/misc/docker/go/Dockerfile b/misc/docker/go/Dockerfile
index a1b54380a..0d774968c 100644
--- a/misc/docker/go/Dockerfile
+++ b/misc/docker/go/Dockerfile
@@ -7,7 +7,8 @@ RUN apt-get -y --no-install-recommends install ca-certificates libc6-dev
 RUN apt-get -y --no-install-recommends install git
 
 # Get Go stable release
+ENV GOLANG_VERSION 1.13.5
 WORKDIR /tmp
-RUN curl -O https://storage.googleapis.com/golang/go1.13.1.linux-amd64.tar.gz
-RUN echo '94f874037b82ea5353f4061e543681a0e79657f787437974214629af8407d124  go1.13.1.linux-amd64.tar.gz' | sha256sum -c
-RUN tar -C /usr/local -xzf go1.13.1.linux-amd64.tar.gz
+RUN curl -O https://storage.googleapis.com/golang/go${GOLANG_VERSION}.linux-amd64.tar.gz
+RUN echo '512103d7ad296467814a6e3f635631bd35574cab3369a97a323c9a585ccaa569  go'${GOLANG_VERSION}'.linux-amd64.tar.gz' | sha256sum -c
+RUN tar -C /usr/local -xzf go${GOLANG_VERSION}.linux-amd64.tar.gz