diff --git a/jflex.spec b/jflex.spec
index 6204fe6..f9d04b3 100644
--- a/jflex.spec
+++ b/jflex.spec
@@ -76,6 +76,7 @@ This package provides %{summary}.
 sed -i /%%inputstreamctor/d src/main/jflex/LexScan.flex
 
 %build
+%{?jpb_env}
 cup -parser LexParse -interface -destdir src/main/java src/main/cup/LexParse.cup
 jflex -d src/main/java/jflex --skel src/main/jflex/skeleton.nested src/main/jflex/LexScan.flex
 %mvn_build