diff --git a/Dockerfile b/Dockerfile
index 95062d7..6484d1a 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -16,6 +16,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     zlib1g-dev \
     libffi-dev \
     libyaml-dev \
+    libpq-dev \
     && rm -rf /var/lib/apt/lists/*
 
 # --- rbenv (installed into home volume on first run, via entrypoint) ---