diff --git a/.github/workflows/csharp.yml b/.github/workflows/csharp.yml
index 1c2f3486..52bb1be4 100644
--- a/.github/workflows/csharp.yml
+++ b/.github/workflows/csharp.yml
@@ -14,7 +14,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        net_version: [1, 2, 3, 4, 5, 6, 7, 8]
+        net_version: [5, 6, 7, 8]
         os: [ubuntu-latest]
         include:
         - net_version: 6
@@ -23,6 +23,14 @@ jobs:
           os: macos-13
         - net_version: 6
           os: windows-latest
+        - net_version: 1
+          os: ubuntu-20.04
+        - net_version: 2
+          os: ubuntu-20.04
+        - net_version: 3
+          os: ubuntu-20.04
+        - net_version: 4
+          os: ubuntu-20.04
     runs-on: ${{ matrix.os }}
 
     steps: