diff --git a/.github/workflows/benchmark.yml b/.github/workflows/benchmark.yml
index 57b36ed9..944788d5 100644
--- a/.github/workflows/benchmark.yml
+++ b/.github/workflows/benchmark.yml
@@ -8,7 +8,7 @@ jobs:
     if: "!contains(github.event.head_commit.message, '[skip ci]')"
     env:
       GKS_ENCODING: "utf8"
-      GKSwstype: 100
+      GKSwstype: "100"
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index ad8a5b7d..797cc072 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -13,7 +13,7 @@ jobs:
     if: "!contains(github.event.head_commit.message, '[skip ci]')"
     env:
       GKS_ENCODING: "utf8"
-      GKSwstype: 100
+      GKSwstype: "100"
 
     name: Julia ${{ matrix.version }} - ${{ matrix.os }}
     runs-on: ${{ matrix.os }}