diff --git a/cannon/Dockerfile.diff b/cannon/Dockerfile.diff
index 33a90202a8905..c4f29a3ab1000 100644
--- a/cannon/Dockerfile.diff
+++ b/cannon/Dockerfile.diff
@@ -1,6 +1,10 @@
 FROM golang:1.24.10-alpine3.21 AS builder
 
-RUN apk add --no-cache bash just
+# Install just from GitHub releases to match the version pinned in mise.toml.
+# The Alpine package is too old and doesn't support the [script] attribute
+# used in testdata justfiles.
+RUN apk add --no-cache bash curl && \
+    curl -sSf https://just.systems/install.sh | bash -s -- --to /usr/local/bin --tag 1.46.0
 
 COPY ./go.mod /app/go.mod
 COPY ./go.sum /app/go.sum