diff --git a/sat4j.spec b/sat4j.spec
index ed57701..3b969f7 100644
--- a/sat4j.spec
+++ b/sat4j.spec
@@ -30,6 +30,7 @@ without worrying about the details.
 %patch0 -p1
 
 %build
+export ANT_OPTS="-Dfile.encoding=iso-8859-1"
 ant -Dbuild.compiler=modern -Drelease=%{version} \
  -Dtarget=1.8 -Dsource=1.8 -DBUILD_DATE=%{build_date} p2