diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 0c37e03c..f5868e17 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -25,7 +25,7 @@ jobs:
           - '1.0'
           - '1.6'
           - '~1.7.0-rc1'
-          # - 'nightly'  # TODO: reenable
+          - 'nightly'
         exclude:
           - os: ubuntu-latest
             architecture: x86
diff --git a/src/julia/core.py b/src/julia/core.py
index 98d72c0c..9d54d108 100644
--- a/src/julia/core.py
+++ b/src/julia/core.py
@@ -564,6 +564,11 @@ def _is_unboxable_as(self, pointer, c_type):
         actual = self.api.jl_typeof(pointer)
         return actual == desired
 
+    # `_unbox_as` was added for communicating with Julia runtime before
+    # initializing PyCal:
+    # * Fail with a helpful message if separate cache is not supported
+    #   https://github.com/JuliaPy/pyjulia/pull/186
+    # However, this is not used anymore at the moment. Maybe clean this up?
     def _unbox_as(self, pointer, c_type):
         self._check_unboxable(c_type)
         jl_unbox = getattr(self.api, 'jl_unbox_{}'.format(c_type))
diff --git a/src/julia/libjulia.py b/src/julia/libjulia.py
index 27a6433d..fb06693c 100644
--- a/src/julia/libjulia.py
+++ b/src/julia/libjulia.py
@@ -64,8 +64,14 @@ def setup_libjulia(libjulia):
             ),
         )
 
-    libjulia.jl_typeof.argtypes = [c_void_p]
-    libjulia.jl_typeof.restype = c_void_p
+    # This does not exist in Julia 1.8 anymore:
+    try:
+        jl_typeof = libjulia.jl_typeof
+    except AttributeError:
+        pass
+    else:
+        jl_typeof.argtypes = [c_void_p]
+        jl_typeof.restype = c_void_p
 
     libjulia.jl_exception_clear.restype = None
     libjulia.jl_stderr_obj.argtypes = []
diff --git a/src/julia/tests/test_sysimage.py b/src/julia/tests/test_sysimage.py
index 9c79834b..67eb9a63 100644
--- a/src/julia/tests/test_sysimage.py
+++ b/src/julia/tests/test_sysimage.py
@@ -16,6 +16,11 @@ def skip_early_julia_versions(juliainfo):
         pytest.skip("Julia < 1.3.1 is not supported")
 
 
+def skip_julia_nightly(juliainfo):
+    if juliainfo.version_info >= (1, 8):
+        pytest.skip("custom sysimage with Julia >= 1.8 (nightly) is not supported")
+
+
 def assert_sample_julia_code_runs(juliainfo, sysimage_path):
     very_random_string = "4903dc03-950f-4a54-98a3-c57a354b62df"
     proc = runcode(
@@ -48,6 +53,7 @@ def assert_sample_julia_code_runs(juliainfo, sysimage_path):
 @pytest.mark.parametrize("with_pycall_cache", [False, True])
 def test_build_and_load(tmpdir, juliainfo, with_pycall_cache):
     skip_early_julia_versions(juliainfo)
+    skip_julia_nightly(juliainfo)
 
     if with_pycall_cache:
         build_pycall(julia=juliainfo.julia)
@@ -75,6 +81,7 @@ def test_build_and_load(tmpdir, juliainfo, with_pycall_cache):
 @skip_in_apple
 def test_build_with_basesysimage_and_load(tmpdir, juliainfo):
     skip_early_julia_versions(juliainfo)
+    skip_julia_nightly(juliainfo)
 
     sysimage_path = str(tmpdir.join("sys.so"))
     base_sysimage_path = juliainfo.sysimage