diff --git a/cmake/toolchain/heptools-dev-base.cmake b/cmake/toolchain/heptools-dev-base.cmake
index d0bc5a821f0999ec9901527e9dbf788d149cc890..cf65a51b900330575a2c35e4bbd3771ce6f05e56 100644
--- a/cmake/toolchain/heptools-dev-base.cmake
+++ b/cmake/toolchain/heptools-dev-base.cmake
@@ -317,7 +317,7 @@ LCG_external_package(PyHEADTAIL        1.12.4
 LCG_external_package(pyjapc            1.5.6                                    )
 LCG_external_package(pyparsing         2.2.0                                    )
 LCG_external_package(pyqt5             5.12                                     )
-IF(${LCG_OS} STREQUAL centos) # libc on slc6 is too old
+IF(${LCG_OS} STREQUAL centos) # libc on slc6 is too old; qtwebengine is blacklisted on mac/ubuntu
   LCG_external_package(pyqtwebengine     5.12.1                                   )
 endif()
 LCG_external_package(pystan            2.17.1.0                                 )
diff --git a/externals/CMakeLists.txt b/externals/CMakeLists.txt
index addb49ef2089937eef6adad6ac1bf0a5d5c2c9de..ec0886533258f42dfcf83a3dc38230d3ef7926c7 100644
--- a/externals/CMakeLists.txt
+++ b/externals/CMakeLists.txt
@@ -1224,7 +1224,7 @@ endif()
 if(LCG_TARGET MATCHES "icc" AND LCG_TARGET MATCHES "slc6")
   set(Qt5_extra_config_opts -platform linux-icc -L/afs/cern.ch/sw/IntelSoftware/linux/x86_64/xe2013/composer_xe_2013_sp1.1.106/compiler/lib/intel64)
 endif()
-if (Python_native_version VERSION_GREATER 3)
+if (Python_native_version VERSION_GREATER 3 OR LCG_COMP MATCHES "clang")
     set(Qt5_qtwebengine -skip qtwebengine)
 endif()