diff --git a/src/lib_aux.c b/src/lib_aux.c
index 104888bd..f25ab65a 100644
--- a/src/lib_aux.c
+++ b/src/lib_aux.c
@@ -314,8 +314,11 @@ LUALIB_API int luaL_loadstring(lua_State *L, const char *s)
 
 static int panic(lua_State *L)
 {
-  fprintf(stderr, "PANIC: unprotected error in call to Lua API (%s)\n",
-	  lua_tostring(L, -1));
+  const char *s = lua_tostring(L, -1);
+  fputs("PANIC: unprotected error in call to Lua API (", stderr);
+  fputs(s ? s : "?", stderr);
+  fputc(')', stderr); fputc('\n', stderr);
+  fflush(stderr);
   return 0;
 }
 
@@ -366,7 +369,7 @@ LUALIB_API lua_State *luaL_newstate(void)
 LUA_API lua_State *lua_newstate(lua_Alloc f, void *ud)
 {
   UNUSED(f); UNUSED(ud);
-  fprintf(stderr, "Must use luaL_newstate() for 64 bit target\n");
+  fputs("Must use luaL_newstate() for 64 bit target\n", stderr);
   return NULL;
 }
 #endif
diff --git a/src/lj_vmevent.c b/src/lj_vmevent.c
index 5a74a5b0..a92cc5d0 100644
--- a/src/lj_vmevent.c
+++ b/src/lj_vmevent.c
@@ -46,8 +46,9 @@ void lj_vmevent_call(lua_State *L, ptrdiff_t argbase)
   if (LJ_UNLIKELY(status)) {
     /* Really shouldn't use stderr here, but where else to complain? */
     L->top--;
-    fprintf(stderr, "VM handler failed: %s\n",
-	    tvisstr(L->top) ? strVdata(L->top) : "?");
+    fputs("VM handler failed: ", stderr);
+    fputs(tvisstr(L->top) ? strVdata(L->top) : "?", stderr);
+    fputc('\n', stderr);
   }
   hook_restore(g, oldh);
   if (g->vmevmask != VMEVENT_NOCACHE)