diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 3064bc20b..394e10047 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -79,8 +79,8 @@ jobs:
           echo "SDKROOT: ${SDKROOT}"
           echo "SDKROOT=${SDKROOT}" >> $GITHUB_ENV
           echo "CONDA_BUILD_SYSROOT=${SDKROOT}" >> $GITHUB_ENV
-          echo "CFLAGS=-I/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include" >> $GITHUB_ENV
-          echo "LDFLAGS=-L/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/lib" >> $GITHUB_ENV
+          echo "CFLAGS=-I${SDKROOT}/usr/include" >> $GITHUB_ENV
+          echo "LDFLAGS=-L${SDKROOT}/usr/lib" >> $GITHUB_ENV
 
       - name: Set current date as environment variable
         run: echo "TODAY=$(date +'%Y.%m.%d')" >> $GITHUB_ENV
diff --git a/benchmarks/conftest.py b/benchmarks/conftest.py
index 311b28d29..b5bb3c9fc 100644
--- a/benchmarks/conftest.py
+++ b/benchmarks/conftest.py
@@ -1,6 +1,7 @@
 """Config file for pytest. Allow caching for faster test completion.
 `$ pytest tests/ --use-cache`
 """
+import pytest
 
 
 def pytest_addoption(parser):
@@ -11,3 +12,37 @@ def pytest_generate_tests(metafunc):
     if metafunc.config.getoption("use_cache"):
         import pyccl
         pyccl.Caching.enable()
+
+
+def _isitgr_unusable_reason():
+    """Return why isitgr cannot be used (None if it can). An installed
+    but unloadable isitgr (e.g. an invalid shared library) raises OSError,
+    not ImportError."""
+    try:
+        import isitgr  # noqa: F401
+    except (ImportError, OSError) as exc:
+        return f"isitgr is not usable: {exc!r}"
+    return None
+
+
+_ISITGR_REASON = _isitgr_unusable_reason()
+_USES_ISITGR = {}
+
+
+def _module_uses_isitgr(path):
+    # The isitgr transfer function is requested inside the tests, not through
+    # a pytest parameter, so look at the source of the test module.
+    if path not in _USES_ISITGR:
+        _USES_ISITGR[path] = "boltzmann_isitgr" in path.read_text(
+            encoding="utf-8")
+    return _USES_ISITGR[path]
+
+
+def pytest_collection_modifyitems(config, items):
+    # Skip the benchmarks that need a working isitgr when it is unavailable.
+    if _ISITGR_REASON is None:
+        return
+    skip = pytest.mark.skip(reason=_ISITGR_REASON)
+    for item in items:
+        if _module_uses_isitgr(item.path):
+            item.add_marker(skip)
diff --git a/pyccl/boltzmann.py b/pyccl/boltzmann.py
index 7f0e76407..bb337ff75 100644
--- a/pyccl/boltzmann.py
+++ b/pyccl/boltzmann.py
@@ -4,7 +4,7 @@
 
 try:
     import isitgr  # noqa: F401
-except ModuleNotFoundError:
+except (ImportError, OSError):
     pass  # prevent nans from isitgr
 
 from . import CCLError, Pk2D, check, lib, sigma8
diff --git a/pyccl/tests/conftest.py b/pyccl/tests/conftest.py
index 7e68afe4f..6cdbc2562 100644
--- a/pyccl/tests/conftest.py
+++ b/pyccl/tests/conftest.py
@@ -1,6 +1,8 @@
 """Config file for pytest. Allow caching for faster test completion.
 `$ pytest tests/ --use-cache`
 """
+import pytest
+
 from .test_cclobject import all_subclasses, init_decorator
 import pyccl
 
@@ -15,6 +17,36 @@ def pytest_generate_tests(metafunc):
         pyccl.Caching.enable()
 
 
+def _isitgr_unusable_reason():
+    """Return why isitgr cannot be used (None if it can). An installed
+    but unloadable isitgr (e.g. an invalid shared library) raises OSError,
+    not ImportError."""
+    try:
+        import isitgr  # noqa: F401
+    except (ImportError, OSError) as exc:
+        return f"isitgr is not usable: {exc!r}"
+    return None
+
+
+_ISITGR_REASON = _isitgr_unusable_reason()
+
+
+def pytest_collection_modifyitems(config, items):
+    # Skip the tests that need a working isitgr when it is unavailable.
+    if _ISITGR_REASON is None:
+        return
+    skip = pytest.mark.skip(reason=_ISITGR_REASON)
+    for item in items:
+        callspec = getattr(item, "callspec", None)
+        if callspec is None:
+            continue
+        # Only compare string parameters: other parameters may be arrays,
+        # for which `==` would not return a single bool.
+        if any(isinstance(val, str) and val == "boltzmann_isitgr"
+               for val in callspec.params.values()):
+            item.add_marker(skip)
+
+
 # For testing, we want to make sure that all instances of the subclasses
 # of `CCLAutoRepr` contain all attributes listed in `__repr_attrs__`.
 # We run some things post-init for these subclasses, which are triggered
diff --git a/pyccl/tests/test_power_mu_sigma_sigma8norm.py b/pyccl/tests/test_power_mu_sigma_sigma8norm.py
index 55fb1732d..c73ce211c 100644
--- a/pyccl/tests/test_power_mu_sigma_sigma8norm.py
+++ b/pyccl/tests/test_power_mu_sigma_sigma8norm.py
@@ -94,3 +94,15 @@ def test_nonlin_camb_MG_error():
     # Check that non-linear power spectrum isn't being used with sigma8
     with pytest.raises(ValueError):
         ccl.nonlin_matter_power(ccl_cosmo, k, 1.0)
+
+
+def test_import_survives_broken_isitgr(tmp_path, monkeypatch):
+    """An installed but unloadable isitgr (e.g. an invalid shared library
+    raising OSError at import) must not prevent importing pyccl."""
+    pkg = tmp_path / "isitgr"
+    pkg.mkdir()
+    (pkg / "__init__.py").write_text("raise OSError('invalid shared lib')\n")
+    monkeypatch.syspath_prepend(str(tmp_path))
+    with mock.patch.dict(sys.modules):
+        sys.modules.pop("isitgr", None)
+        reload(ccl.boltzmann)