diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index a2e10cc0..d8522b76 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -18,6 +18,7 @@ jobs:
       fail-fast: false
       matrix:
         version:
+          - '1.6'  # older supported LTS
           - '1.10'  # latest LTS
           - '1'
         experimental:
diff --git a/.github/workflows/invalidations.yml b/.github/workflows/invalidations.yml
deleted file mode 100644
index 0dc819ad..00000000
--- a/.github/workflows/invalidations.yml
+++ /dev/null
@@ -1,41 +0,0 @@
-name: invalidations
-
-on:
-  pull_request:
-  push:
-   branches: [main]
-
-concurrency: 
-  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
-  cancel-in-progress: true
-
-jobs:
-  check:
-    runs-on: ubuntu-latest
-    steps:
-    - uses: julia-actions/setup-julia@latest
-      with:
-        version: '1'
-    - uses: actions/checkout@v4
-    - uses: julia-actions/julia-buildpkg@latest
-    - uses: julia-actions/julia-invalidations@v1
-      id: invs_pr
-
-    - uses: actions/checkout@v4
-      with:
-        ref: 'main'
-    - uses: julia-actions/julia-buildpkg@latest
-    - uses: julia-actions/julia-invalidations@v1
-      id: invs_main
-
-    - name: Report invalidation counts
-      run: |
-        echo "Invalidations on main: ${{ steps.invs_main.outputs.total }} (${{ steps.invs_main.outputs.deps }} via deps)"
-        echo "This branch: ${{ steps.invs_pr.outputs.total }} (${{ steps.invs_pr.outputs.deps }} via deps)"
-      shell: bash
-    - name: PR doesn't increase number of invalidations
-      run: |
-        if (( ${{ steps.invs_pr.outputs.total }} > ${{ steps.invs_main.outputs.total }} )); then
-            exit 1
-        fi
-      shell: bash
diff --git a/Project.toml b/Project.toml
index 4762efd0..d873cbb5 100644
--- a/Project.toml
+++ b/Project.toml
@@ -42,7 +42,7 @@ StaticArrays = "1"
 StatsBase = "0.33, 0.34"
 Term = "2"
 Unitful = "1"
-julia = "1.10"
+julia = "1.6"
 
 [extensions]
 FreeTypeExt = ["FileIO", "FreeType"]
diff --git a/test/tst_issues.jl b/test/tst_issues.jl
index 9fd7318b..5a6e607e 100644
--- a/test/tst_issues.jl
+++ b/test/tst_issues.jl
@@ -89,31 +89,21 @@
         y = @. 2x * u"s"
         ylim = (0u"s", 8u"s")
 
-        p = lineplot(x, y; ylim)
-        show(devnull, p)
-
-        p = scatterplot(x, y; ylim)
-        show(devnull, p)
+        @test lineplot(x, y; ylim) isa Plot
+        @test scatterplot(x, y; ylim) isa Plot
     end
 
     @testset "Unitful dispatch (#383)" begin
-        p = lineplot(rand(1), rand(1) * u"m")
-        show(devnull, p)
-        p = lineplot(rand(1) * u"m", rand(1))
-        show(devnull, p)
-
-        p = scatterplot(rand(1), rand(1) * u"m")
-        show(devnull, p)
-        p = scatterplot(rand(1) * u"m", rand(1))
-        show(devnull, p)
+        @test lineplot(rand(1), rand(1) * u"m") isa Plot
+        @test lineplot(rand(1) * u"m", rand(1)) isa Plot
+
+        @test scatterplot(rand(1), rand(1) * u"m") isa Plot
+        @test scatterplot(rand(1) * u"m", rand(1)) isa Plot
     end
 
     @testset "Heatmap ±Inf (#378)" begin
-        p = heatmap([1 2; 3 -Inf])
-        show(devnull, p)
-        p = heatmap([-Inf;;])
-        show(devnull, p)
-        p = heatmap([1 2; 3 Inf])
-        show(devnull, p)
+        @test heatmap([1 2; 3 -Inf]) isa Plot
+        @test heatmap([-Inf]') isa Plot
+        @test heatmap([1 2; 3 Inf]) isa Plot
     end
 end