diff --git a/src/lib/lua-cjson/strbuf.c b/src/lib/lua-cjson/strbuf.c
index c3272f09..5b28e3f0 100644
--- a/src/lib/lua-cjson/strbuf.c
+++ b/src/lib/lua-cjson/strbuf.c
@@ -95,7 +95,7 @@ static inline void debug_stats(strbuf_t *s)
 {
     if (s->debug) {
         fprintf(stderr, "strbuf(%p) reallocs: %d, length: %d, size: %d\n",
-                s, s->reallocs, s->length, s->size);
+                (void*) s, s->reallocs, s->length, s->size);
     }
 }
 
@@ -169,7 +169,7 @@ void strbuf_resize(strbuf_t *s, int len)
 
     if (s->debug > 1) {
         fprintf(stderr, "strbuf(%p) resize: %d => %d\n",
-                s, s->size, newsize);
+                (void*) s, s->size, newsize);
     }
 
     s->size = newsize;