diff --git a/sdformat.spec b/sdformat.spec
index 0acf8d8..71ac284 100644
--- a/sdformat.spec
+++ b/sdformat.spec
@@ -63,12 +63,11 @@ The %{name}-doc package contains development documentation for
 %patch1 -p1
 # Remove bundled urdf components
 rm -rf src/urdf
+sed -i 's/unset/#unset/g' CMakeLists.txt
 
 %build
 %cmake \
   -DCMAKE_BUILD_TYPE=Release \
-  -DCMAKE_C_FLAGS_RELWITHDEBINFO="-std=c++11 %{optflags}" \
-  -DCMAKE_CXX_FLAGS_RELWITHDEBINFO="-std=c++11 %{optflags}" \
   -DLIB_INSTALL_DIR:STRING=%{_lib} \
   -DRUBY_LIB_INSTALL_DIR:STRING=%{ruby_vendorlibdir} \
   -DUSE_EXTERNAL_URDF=ON \