diff --git a/target-ppc/helper.h b/target-ppc/helper.h
index 5cf6cd4..c025a2f 100644
--- a/target-ppc/helper.h
+++ b/target-ppc/helper.h
@@ -95,6 +95,7 @@
 
 #define dh_alias_avr ptr
 #define dh_ctype_avr ppc_avr_t *
+#define dh_is_signed_avr dh_is_signed_ptr
 
 DEF_HELPER_3(vaddubm, void, avr, avr, avr)
 DEF_HELPER_3(vadduhm, void, avr, avr, avr)