diff --git a/debian/rules b/debian/rules
index 74f3c7b8..a5061352 100755
--- a/debian/rules
+++ b/debian/rules
@@ -62,7 +62,7 @@ endif
 POLLY_ENABLE=no
 ifeq ($(shell dpkg --compare-versions $(shell dpkg-query -W -f '$${Version}' libisl-dev) ge 0.12.1; echo $$?),0)
 ifeq ($(shell dpkg --compare-versions $(shell dpkg-query -W -f '$${Version}' libcloog-isl-dev) ge 0.18.1; echo $$?),0)
-POLLY_ENABLE=YES
+POLLY_ENABLE=yes
 endif
 endif