diff --git a/Dockerfile b/Dockerfile
new file mode 100644
index 0000000..d04164c
--- /dev/null
+++ b/Dockerfile
@@ -0,0 +1,7 @@
+FROM python:3.6
+
+COPY requirements-py3.txt requirements.txt
+
+RUN set -ex &&\
+    apt-get update && apt-get install -y virtualenv &&\
+    pip install --upgrade -r requirements.txt
diff --git a/bitmath/__init__.py b/bitmath/__init__.py
index 6babc18..d24ce58 100644
--- a/bitmath/__init__.py
+++ b/bitmath/__init__.py
@@ -1341,7 +1341,7 @@ def getsize(path, bestprefix=True, system=NIST):
 instances back.
     """
     _path = os.path.realpath(path)
-    size_bytes = os.path.getsize(_path)
+    size_bytes = os.stat(_path).st_size
     if bestprefix:
         return Byte(size_bytes).best_prefix(system=system)
     else:
diff --git a/docker-compose.yaml b/docker-compose.yaml
new file mode 100644
index 0000000..7c510e3
--- /dev/null
+++ b/docker-compose.yaml
@@ -0,0 +1,13 @@
+---
+
+version: '3.8'
+services:
+  bitmath:
+    build:
+      context: .
+      dockerfile: Dockerfile
+    working_dir: /app
+    volumes:
+      - .:/app
+    command: make unittests pycodestyle pyflakes
+    tty: true