diff --git a/.tool-versions b/.tool-versions
index 4933a41..f526442 100644
--- a/.tool-versions
+++ b/.tool-versions
@@ -1 +1 @@
-golang 1.18
+golang 1.22.0
diff --git a/Dockerfile b/Dockerfile
index 791a922..f922758 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -2,7 +2,7 @@
 ###############################
 # Build the doctree Go binary #
 ###############################
-FROM golang:1.18-alpine as builder
+FROM golang:1.21-alpine@sha256:7d43edac318983a0ec945494efdc11cc824ae995226846f3dc7acfdb2b445b67 as builder
 
 RUN apk add --no-cache git build-base
 COPY . /doctree