diff --git a/luprex/core/cpp/printbuffer.cpp b/luprex/core/cpp/printbuffer.cpp
index ef823390..55d029fb 100644
--- a/luprex/core/cpp/printbuffer.cpp
+++ b/luprex/core/cpp/printbuffer.cpp
@@ -191,7 +191,7 @@ bool PrintChanneler::channel(const PrintBuffer *printbuffer, std::ostream &ostre
 
 Invocation PrintChanneler::invocation(int64_t actor_id) {
     char buf[80];
-    sprintf(buf, PRId64, line_);
+    sprintf(buf, "%" PRId64, line_);
     return Invocation(Invocation::KIND_FLUSH_PRINTS, actor_id, actor_id, buf, InvocationData());
 }