diff --git a/upb/port_def.inc b/upb/port_def.inc
index 2c144dc066..7371b6d456 100644
--- a/upb/port_def.inc
+++ b/upb/port_def.inc
@@ -79,6 +79,10 @@
 #define UPB_FORCEINLINE __inline__ __attribute__((always_inline))
 #define UPB_NOINLINE __attribute__((noinline))
 #define UPB_NORETURN __attribute__((__noreturn__))
+#elif defined(_MSC_VER)
+#define UPB_NOINLINE
+#define UPB_FORCEINLINE
+#define UPB_NORETURN __declspec(noreturn)
 #else  /* !defined(__GNUC__) */
 #define UPB_FORCEINLINE
 #define UPB_NOINLINE