diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 0502e87..5e7930d 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -41,8 +41,9 @@ jobs:
           - os: macos-latest
             version: '1.6'
         include:
-          - version: 'nightly'
-            os: ubuntu-latest
+          - os: ubuntu-latest
+            version: 'nightly'
+            arch: x64
             experimental: true
 
     steps:
@@ -50,6 +51,7 @@ jobs:
       - uses: julia-actions/setup-julia@latest
         with:
           version: ${{ matrix.version }}
+          arch: ${{ matrix.arch }}
       - uses: julia-actions/cache@v1
       - uses: julia-actions/julia-buildpkg@latest
       - uses: julia-actions/julia-runtest@latest
diff --git a/test/runtests.jl b/test/runtests.jl
index 95ddac9..843868a 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -14,6 +14,11 @@ warn_ticks = :warn, "No strict ticks found"
 const C = RGBA{Float64}
 const C0 = RGBA{PlotUtils.Colors.N0f8}
 
+bool_env(x, default::String = "0")::Bool = tryparse(Bool, get(ENV, x, default))
+
+is_ci() = bool_env("CI")
+is_64b() = Sys.WORD_SIZE == 64
+
 @testset "colors" begin
     @test plot_color(nothing) == C(0, 0, 0, 0)
     @test plot_color(false) == C(0, 0, 0, 0)
@@ -120,7 +125,8 @@ end
     @test optimize_ticks(-1, 2) == ([-1.0, 0.0, 1.0, 2.0], -1.0, 2.0)
 
     # check if ticks still generate if max - min << abs(min) (i.e. for Float64 ranges)
-    @test optimize_ticks(1e11 - 1, 1e11 + 2) == (1e11 .+ (-1:2), 1e11 - 1.0, 1e11 + 2.0)
+    is_64b() &&
+        @test optimize_ticks(1e11 - 1, 1e11 + 2) == (1e11 .+ (-1:2), 1e11 - 1.0, 1e11 + 2.0)
 
     @testset "dates" begin
         dt1, dt2 = Dates.value(DateTime(2000)), Dates.value(DateTime(2100))
@@ -158,6 +164,7 @@ end
 
     @testset "digits" begin
         @testset "digits $((10^n) - 1)*10^$i" for n ∈ 1:9, i ∈ -9:9
+            (!is_64b() && n ≥ 9) && continue
             y0 = 10^n
             x0 = y0 - 1
             x, y = (x0, y0) .* 10.0^i
@@ -314,7 +321,16 @@ end
     @test stats.time < 1e-3  # ~ 0.22ms (on 1.9)
 end
 
-if Sys.islinux() && VERSION ≥ v"1.9.0" && isempty(VERSION.prerelease)  # avoid running on `nightly`
+if (
+    Sys.islinux() &&
+    VERSION ≥ v"1.11.0" &&
+    isempty(VERSION.prerelease) &&  # avoid running on `nightly`
+    is_64b() &&
+    (
+        !is_ci() ||
+        (is_ci() && get(ENV, "GITHUB_EVENT_NAME", "pull_request") == "pull_request")
+    )
+)
     @testset "downstream" begin
         include("downstream.jl")
     end