diff --git a/mobidict.spec b/mobidict.spec
index 03eaacd..acfbdf3 100644
--- a/mobidict.spec
+++ b/mobidict.spec
@@ -46,6 +46,7 @@ patch -p1 < ../libmobi.patch
 patch -p1 < ../update-enc-length.patch
 
 %build
+export CFLAGS="%{optflags} -std=c11"
 %define __builder ninja
 %cmake