diff --git a/firefox.spec b/firefox.spec
index 6fd54ac..fdd294e 100644
--- a/firefox.spec
+++ b/firefox.spec
@@ -1116,6 +1116,9 @@ 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.