diff --git a/.github/workflows/test-wheel-linux.yml b/.github/workflows/test-wheel-linux.yml
index 0bb470b26c3..e328939d052 100644
--- a/.github/workflows/test-wheel-linux.yml
+++ b/.github/workflows/test-wheel-linux.yml
@@ -128,6 +128,10 @@ jobs:
     steps:
       - name: Checkout ${{ github.event.repository.name }}
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1  # v7.0.1
+        with:
+          # Test sources must match the wheels under test (nightly runs
+          # reuse wheels built from an older commit of main).
+          ref: ${{ inputs.sha || github.sha }}
 
       - name: Setup proxy cache
         uses: nv-gha-runners/setup-proxy-cache@main
diff --git a/.github/workflows/test-wheel-windows.yml b/.github/workflows/test-wheel-windows.yml
index 7abfc74126b..8256981bff8 100644
--- a/.github/workflows/test-wheel-windows.yml
+++ b/.github/workflows/test-wheel-windows.yml
@@ -107,6 +107,10 @@ jobs:
     steps:
       - name: Checkout ${{ github.event.repository.name }}
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1  # v7.0.1
+        with:
+          # Test sources must match the wheels under test (nightly runs
+          # reuse wheels built from an older commit of main).
+          ref: ${{ inputs.sha || github.sha }}
 
       - name: Setup proxy cache
         uses: nv-gha-runners/setup-proxy-cache@main
diff --git a/cuda_bindings/tests/test_cuda.py b/cuda_bindings/tests/test_cuda.py
index 80ac5da0fd0..65212efbcb7 100644
--- a/cuda_bindings/tests/test_cuda.py
+++ b/cuda_bindings/tests/test_cuda.py
@@ -655,6 +655,8 @@ def test_ffi_coverage_jit_option_binary_loader_thread_count():
 def test_ffi_coverage_jit_wall_time_pointer_is_valid():
     """CU_JIT_WALL_TIME must give CUDA a valid writable float address, not a garbage pointer."""
     helper = cuda._HelperCUjit_option(cuda.CUjit_option.CU_JIT_WALL_TIME, 0.0)
+    # Guard against NULL so a regression fails instead of segfaulting.
+    assert helper.cptr != 0
     # Write a sentinel float via ctypes to confirm the pointer is addressable.
     ctypes.c_float.from_address(helper.cptr).value = 3.14
     assert ctypes.c_float.from_address(helper.cptr).value == pytest.approx(3.14, rel=1e-5)