diff --git a/netdissect-stdinc.h b/netdissect-stdinc.h
index 9cf3cf07..5aef8234 100644
--- a/netdissect-stdinc.h
+++ b/netdissect-stdinc.h
@@ -148,23 +148,12 @@
         #define PRIu64	"llu"
       #endif
     #endif
-
-    /*
-     * MSVC's support library doesn't support %zu to print a size_t until
-     * Visual Studio 2017, but supports %Iu earlier, so use that.
-     */
-    #define PRIsize	"Iu"
   #elif defined(__MINGW32__) || !defined(_WIN32)
     /*
      * Compiler is MinGW or target is UN*X or MS-DOS.  Just use
      * <inttypes.h>.
      */
     #include <inttypes.h>
-
-    /*
-     * Assume the support library supports %zu; it's required by C99.
-     */
-    #define PRIsize	"zu"
   #endif
 #endif /* HAVE_PCAP_PCAP_INTTYPES_H */