diff --git a/include/bx/macros.h b/include/bx/macros.h
index b403e7a..108aa49 100644
--- a/include/bx/macros.h
+++ b/include/bx/macros.h
@@ -68,7 +68,7 @@
 #define BX_ALIGN_STRUCT_16(_struct) BX_ALIGN_STRUCT(16, _struct)
 #define BX_ALIGN_STRUCT_256(_struct) BX_ALIGN_STRUCT(256, _struct)
 
-#define BX_UNUSED_1(_a1) do { (void)sizeof(_a1); } while(0)
+#define BX_UNUSED_1(_a1) do { (void)(true ? (void)0 : ( (void)(_a1) ) ); } while(0)
 #define BX_UNUSED_2(_a1, _a2) BX_UNUSED_1(_a1); BX_UNUSED_1(_a2)
 #define BX_UNUSED_3(_a1, _a2, _a3) BX_UNUSED_2(_a1, _a2); BX_UNUSED_1(_a3)
 #define BX_UNUSED_4(_a1, _a2, _a3, _a4) BX_UNUSED_3(_a1, _a2, _a3); BX_UNUSED_1(_a4)
diff --git a/include/bx/string.h b/include/bx/string.h
index 4ddd249..a2e0c79 100644
--- a/include/bx/string.h
+++ b/include/bx/string.h
@@ -9,6 +9,7 @@
 #include "bx.h"
 #include <alloca.h>
 #include <stdarg.h> // va_list
+#include <stdio.h>  // vsnprintf
 #include <string.h>
 #include <string>