diff --git a/Dockerfile b/Dockerfile
index 14c70f2..cf30b30 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -4,8 +4,8 @@ WORKDIR /usr/src/app
 
 RUN apk add --no-cache git
 
-COPY requirements.txt ./
-RUN pip install --no-cache-dir -r requirements.txt
+COPY requirements.txt constraint.txt ./
+RUN PIP_CONSTRAINT=constraint.txt pip install --no-cache-dir -r requirements.txt
 
 COPY . .
 
diff --git a/constraint.txt b/constraint.txt
new file mode 100644
index 0000000..20f73f1
--- /dev/null
+++ b/constraint.txt
@@ -0,0 +1 @@
+Cython < 3.0