diff --git a/plat/arm/board/juno/juno_decl.h b/plat/arm/board/juno/juno_decl.h
index cd87c3b..21e56c0 100644
--- a/plat/arm/board/juno/juno_decl.h
+++ b/plat/arm/board/juno/juno_decl.h
@@ -7,6 +7,6 @@
 #ifndef JUNO_DECL_H
 #define JUNO_DECL_H
 
-int juno_getentropy(void *buf, size_t len);
+bool juno_getentropy(uint64_t *buf);
 
 #endif /* JUNO_DECL_H */