diff --git a/thunderbird.spec b/thunderbird.spec
index 1d51290..7a1c4d8 100644
--- a/thunderbird.spec
+++ b/thunderbird.spec
@@ -1014,6 +1014,9 @@ echo "ac_add_options --with-mozilla-api-keyfile=`pwd`/mozilla-api-key" >> .mozco
 echo "ac_add_options --with-google-location-service-api-keyfile=`pwd`/google-loc-api-key" >> .mozconfig
 echo "ac_add_options --with-google-safebrowsing-api-keyfile=`pwd`/google-api-key" >> .mozconfig
 
+# Clang 17 upstream's detection fails, tell it where to look.
+echo "ac_add_options --with-libclang-path=`llvm-config --libdir`" >> .mozconfig
+
 echo 'export NODEJS="%{_buildrootdir}/bin/node-stdout-nonblocking-wrapper"' >> .mozconfig
 
 # Remove executable bit to make brp-mangle-shebangs happy.