diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index bd730649e..13c9b5735 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -7,7 +7,7 @@ on:
 
 jobs:
   build:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-18.04 # due to problem with Calibre and Ubuntu 20
     env:
       SHA: ${{ github.sha }}
     steps: