diff --git a/uchardet.spec b/uchardet.spec
index 2b5d49d..5f2cc1e 100644
--- a/uchardet.spec
+++ b/uchardet.spec
@@ -74,10 +74,10 @@ This package contains the development files.
 %build
 mkdir build
 cd build
-export CFLAGS="%{optflags}"
-export CXXFLAGS="%{optflags}"
 cmake .. \
     -DCMAKE_INSTALL_PREFIX=%{_prefix} \
+    -DCMAKE_C_FLAGS="%{optflags}" \
+    -DCMAKE_CXX_FLAGS="%{optflags}" \
     -DCMAKE_INSTALL_LIBDIR=%{_libdir}
 make %{?_smp_mflags} VERBOSE=1