diff --git a/gn.spec b/gn.spec
index a6c5014..ea781ea 100644
--- a/gn.spec
+++ b/gn.spec
@@ -106,6 +106,9 @@ cp -vp misc/vim/README.md README-vim.md
 # Fix shebangs in examples and such.
 %py3_shebang_fix .
 
+# Stop overriding optimization flags
+sed -r -i '/.append(.-O3.)/d' build/gen.py
+
 
 %build
 # We need to set CC and CXX explicitly before Fedora 33, including on the EPELs.