diff --git a/libcxx.spec b/libcxx.spec
index 30a179e..76c31be 100644
--- a/libcxx.spec
+++ b/libcxx.spec
@@ -57,7 +57,7 @@ cd _build
 %endif
 
 # Filter out cflags not supported by clang.
-%global optflags %(echo %{optflags} | sed -e 's/-mcet//g' -e 's/-fcf-protection//g')
+%global optflags %(echo %{optflags} | sed -e 's/-mcet//g' -e 's/-fcf-protection//g' -e 's/-fstack-clash-protection//g')
 
 # Clang in older releases than f24 can't build this code without crashing.
 # So, we use gcc there. But the really old version in RHEL 6 works. Huh.