diff --git a/ci/build-check.sh b/ci/build-check.sh
index 9657313f..589b5d6e 100755
--- a/ci/build-check.sh
+++ b/ci/build-check.sh
@@ -10,11 +10,16 @@ ${dn}/build.sh
 # support parallel runs right now
 /usr/bin/make check
 make install
-git clean -dfx
 
-# And now a clang build to find unused variables
-export CC=clang
-export CFLAGS='-Werror=unused-variable -Werror=maybe-uninitialized'
-build_default
-# don't actually run the tests, just compile them
-/usr/bin/make check TESTS=
+# And now a clang build to find unused variables, but only run on Fedora because
+# the CentOS version is ancient anyway and doesn't support all the flags that
+# might get passed to it.
+id=$(. /etc/os-release && echo $ID)
+if [ "$id" == fedora ]; then
+    git clean -dfx
+    export CC=clang
+    export CFLAGS='-Werror=unused-variable -Werror=maybe-uninitialized'
+    build_default
+    # don't actually run the tests, just compile them
+    /usr/bin/make check TESTS=
+fi