diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 8c94bb8..3883ae5 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -11,7 +11,7 @@ on:
 
 jobs:
   tests:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     strategy:
       matrix:
         python-version: [3.6, 3.7, 3.8, 3.9]
@@ -26,6 +26,8 @@ jobs:
 
       - name: Set up Poetry
         uses: snok/install-poetry@v1
+        with:
+          version: 1.1.10
 
       - name: Install dependencies
         run: |
diff --git a/pyproject.toml b/pyproject.toml
index 8afff84..ba82f6a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -52,5 +52,5 @@ pytest = ">=3.7.1"
 # jupyter_kernel_test==0.3.0
 
 [build-system]
-requires = ["poetry-core>=1.0.0"]
+requires = ["poetry-core>=1.1.10"]
 build-backend = "poetry.core.masonry.api"