diff --git a/cmake/ci.cmake b/cmake/ci.cmake
index 2e01f55f7..834687f57 100644
--- a/cmake/ci.cmake
+++ b/cmake/ci.cmake
@@ -721,10 +721,14 @@ add_custom_target(ci_icpx
 # (needed for the dtoa/grisu and NaN-comparison code paths).
 #
 # The following tests are excluded as they trigger known nvc++ 25.5 defects (not
-# library bugs); see https://github.com/nlohmann/json for tracking:
-#   - test-comparison*       : miscompiles cross-type/<=> comparison (e.g. `-17 <= null`)
-#   - test-constructor1      : std::initializer_list lifetime bug -> SIGSEGV
-#   - test-deserialization   : mangles UTF-8 u8"" string literals
+# library bugs); see https://github.com/nlohmann/json for tracking. Only the
+# affected language-standard variants are excluded so coverage is otherwise kept:
+#   - test-comparison_cpp20, test-comparison_legacy_cpp20
+#         miscompiles cross-type/<=> comparison (e.g. `-17 <= null`)
+#   - test-constructor1_cpp11
+#         std::initializer_list lifetime bug -> SIGSEGV
+#   - test-deserialization_cpp20
+#         mangles the UTF-8 u8"" string literal in the char8_t (C++20) section
 add_custom_target(ci_nvhpc
     COMMAND ${CMAKE_COMMAND}
         -DCMAKE_BUILD_TYPE=Debug -GNinja
@@ -733,7 +737,9 @@ add_custom_target(ci_nvhpc
         -DJSON_BuildTests=ON -DJSON_FastTests=ON
         -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_nvhpc
     COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_nvhpc
-    COMMAND cd ${PROJECT_BINARY_DIR}/build_nvhpc && ${CMAKE_CTEST_COMMAND} --parallel ${N} --exclude-regex "test-unicode|test-comparison|test-constructor1|test-deserialization" --output-on-failure
+    # the pipes are escaped so the surrounding shell passes them to ctest verbatim
+    # instead of treating them as shell pipe operators
+    COMMAND cd ${PROJECT_BINARY_DIR}/build_nvhpc && ${CMAKE_CTEST_COMMAND} --parallel ${N} --exclude-regex "test-unicode\\|test-comparison_cpp20\\|test-comparison_legacy_cpp20\\|test-constructor1_cpp11\\|test-deserialization_cpp20" --output-on-failure
     COMMENT "Compile and test with NVIDIA HPC SDK (nvc++)"
 )