diff --git a/config/cs_auto_flags.sh b/config/cs_auto_flags.sh
index d02f2cf154..562a237142 100644
--- a/config/cs_auto_flags.sh
+++ b/config/cs_auto_flags.sh
@@ -751,10 +751,19 @@ elif test "x$cs_gxx" = "xclang"; then
   cxxflags_default_omp="-fopenmp=libomp"
 
   cs_clangpp_version_number=`echo $cs_ac_cxx_version | sed -e "s/^.*version //"`
-  case "$cs_clangpp_version_number" in
+    case "$cs_ac_cxx_version" in
+    *Apple*)
+      # Apple clang version numbers do not match LLVM ones, and the
+      # default C++ standard remains C++14 in recent versions.
+      cxxflags_default="$cxxflags_default  -std=c++17"
+      ;;
+    *)
+      case "$cs_clangpp_version_number" in
     14* | 15*)
       cxxflags_default="$cxxflags_default  -std=c++17"
       ;;
+  esac
+        ;;
   esac
   case "$cs_clangpp_version_number" in
     14* | 15* | 16* | 17* | 18* | 19* | 2*)
diff --git a/configure.ac b/configure.ac
index a947073c08..7bf7100f07 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1107,7 +1107,7 @@ sys.exit(0)]"
   fi
 
   # Test for PyQt6 developer tools
-  if test "x$cs_have_gui" = "xPyQt5" ; then
+  if test "x$cs_have_gui" = "xPyQt6" ; then
 
     # Try to find PyQt6 tools through Python interpreter
     prog="[import os, sys