diff --git a/src/bindings/perl/Makefile.PL b/src/bindings/perl/Makefile.PL
index 4e457fcd77e2ee230aeccf79080e073d4f6eb493..a629deb570b0fa821d2cf8f4aa26042c7a840871 100644
--- a/src/bindings/perl/Makefile.PL
+++ b/src/bindings/perl/Makefile.PL
@@ -10,6 +10,6 @@ WriteMakefile(
     LIBS => ["-lhammer"],
     OBJECT => 'hammer_wrap.o',
     INC => '-I../..',
-    CCFLAGS => "$Config{ccflags} -DSWIG -std=gnu99",
+    CCFLAGS => "$Config{ccflags} -DSWIG -DHAS_BOOL -std=gnu99",
     );