diff --git a/Dockerfile b/Dockerfile
index 33e77d5..b87c66e 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -7,7 +7,10 @@ WORKDIR /app
 RUN apk add --no-cache ffmpeg curl
 
 COPY package.json ./
-RUN npm install --omit=dev
+# argon2 compiles native code via node-gyp — needs python3/make/g++ at build time
+RUN apk add --no-cache --virtual .build-deps python3 make g++ \
+    && npm install --omit=dev \
+    && apk del .build-deps
 
 COPY . .