diff --git a/.github/workflows/macos.yml b/.github/workflows/macos.yml
index 7718e019db..ee48db79c8 100644
--- a/.github/workflows/macos.yml
+++ b/.github/workflows/macos.yml
@@ -43,14 +43,14 @@ jobs:
       - name: Tests
         run: make -s ${{ matrix.test_task }}
         env:
-          TESTOPTS: "$JOBS -q --tty=no"
+          RUBY_TESTOPTS: "$JOBS -q --tty=no"
           MSPECOPT: "-ff" # not using `-j` because sometimes `mspec -j` silently dies
         if: matrix.test_task != 'test-bundled-gems' && !contains(github.event.head_commit.message, '[ci skip]')
       # test-bundled-gems is separated for marking `continue-on-error` because it randomly fails.
       - name: Tests
         run: make -s ${{ matrix.test_task }}
         env:
-          TESTOPTS: "$JOBS -q --tty=no"
+          RUBY_TESTOPTS: "$JOBS -q --tty=no"
         continue-on-error: true
         if: matrix.test_task == 'test-bundled-gems' && !contains(github.event.head_commit.message, '[ci skip]')
       - name: Leaked Globals
diff --git a/.github/workflows/ubuntu.yml b/.github/workflows/ubuntu.yml
index e1cfa2d22f..a6ec9f9cf7 100644
--- a/.github/workflows/ubuntu.yml
+++ b/.github/workflows/ubuntu.yml
@@ -46,14 +46,14 @@ jobs:
       - name: Tests
         run: make -s ${{ matrix.test_task }}
         env:
-          TESTOPTS: "$JOBS -q --tty=no"
+          RUBY_TESTOPTS: "$JOBS -q --tty=no"
           MSPECOPT: "-ff" # not using `-j` because sometimes `mspec -j` silently dies
         if: matrix.test_task != 'test-bundled-gems' && !contains(github.event.head_commit.message, '[ci skip]')
       # test-bundled-gems is separated for marking `continue-on-error` because it randomly fails.
       - name: Tests (test-bundled-gems)
         run: make -s ${{ matrix.test_task }}
         env:
-          TESTOPTS: "-q --tty=no"
+          RUBY_TESTOPTS: "-q --tty=no"
         continue-on-error: true
         if: matrix.test_task == 'test-bundled-gems' && !contains(github.event.head_commit.message, '[ci skip]')
       - name: Leaked Globals