diff --git a/.github/workflows/verify-on-ubuntu.yml b/.github/workflows/verify-on-ubuntu.yml
index 28aab71..4762bb3 100644
--- a/.github/workflows/verify-on-ubuntu.yml
+++ b/.github/workflows/verify-on-ubuntu.yml
@@ -278,3 +278,23 @@ jobs:
         no_known_hosts: true
     - name: print created files
       run: ls -l ~/.ssh
+  without-no_known_hosts:
+    name: no known_hosts file
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os:
+        - ubuntu-16.04
+        - ubuntu-18.04
+        - ubuntu-20.04
+    steps:
+    - name: Checkout source codes
+      uses: actions/checkout@v2
+    - name: Install SSH key
+      uses: ./.
+      with:
+        key: ${{ secrets.SSH_KEY_PEM }}
+      continue-on-error: true
+    - name: print created files
+      run: ls -l ~/.ssh