Add "/D _U_=" to make _U_ expand to nothing.
diff --git a/Win32/Prj/libpcap.dsp b/Win32/Prj/libpcap.dsp
index 2aa04ba..deafa17 100644
--- a/Win32/Prj/libpcap.dsp
+++ b/Win32/Prj/libpcap.dsp
@@ -41,7 +41,7 @@
 # PROP Intermediate_Dir "Release"
 # PROP Target_Dir ""
 # ADD BASE CPP /nologo /W3 /GX /O2 /D "WIN32" /D "NDEBUG" /D "_MBCS" /D "_LIB" /YX /FD /c
-# ADD CPP /nologo /MT /W3 /GX /O2 /I "../../" /I "../../lbl/" /I "../../bpf/" /I "../include/" /I "../../../../common" /D "YY_NEVER_INTERACTIVE" /D yylval=pcap_lval /D "_USRDLL" /D "LIBPCAP_EXPORTS" /D "HAVE_STRERROR" /D "NDEBUG" /D "__STDC__" /D "INET6" /D "WIN32" /D "_WINDOWS" /D "_MBCS" /D SIZEOF_CHAR=1 /D SIZEOF_SHORT=2 /D SIZEOF_INT=4 /D "HAVE_ADDRINFO" /YX /FD /c
+# ADD CPP /nologo /MT /W3 /GX /O2 /I "../../" /I "../../lbl/" /I "../../bpf/" /I "../include/" /I "../../../../common" /D "YY_NEVER_INTERACTIVE" /D yylval=pcap_lval /D "_USRDLL" /D "LIBPCAP_EXPORTS" /D "HAVE_STRERROR" /D "NDEBUG" /D "__STDC__" /D "INET6" /D "WIN32" /D "_WINDOWS" /D "_MBCS" /D SIZEOF_CHAR=1 /D SIZEOF_SHORT=2 /D SIZEOF_INT=4 /D "HAVE_ADDRINFO" /D _U_= /YX /FD /c
 # ADD BASE RSC /l 0x409 /d "NDEBUG"
 # ADD RSC /l 0x409 /d "NDEBUG"
 BSC32=bscmake.exe
@@ -64,7 +64,7 @@
 # PROP Intermediate_Dir "Debug"
 # PROP Target_Dir ""
 # ADD BASE CPP /nologo /W3 /Gm /GX /ZI /Od /D "WIN32" /D "_DEBUG" /D "_MBCS" /D "_LIB" /YX /FD /GZ /c
-# ADD CPP /nologo /MTd /W3 /Gm /GX /ZI /Od /I "../../" /I "../../lbl/" /I "../../bpf/" /I "../include/" /I "../../../../common" /D "YY_NEVER_INTERACTIVE" /D yylval=pcap_lval /D "_USRDLL" /D "LIBPCAP_EXPORTS" /D "HAVE_STRERROR" /D "_DEBUG" /D "__STDC__" /D "INET6" /D "_WINDOWS" /D "_MBCS" /D SIZEOF_CHAR=1 /D SIZEOF_SHORT=2 /D SIZEOF_INT=4 /D "HAVE_ADDRINFO" /D "WIN32" /YX /FD /GZ /c
+# ADD CPP /nologo /MTd /W3 /Gm /GX /ZI /Od /I "../../" /I "../../lbl/" /I "../../bpf/" /I "../include/" /I "../../../../common" /D "YY_NEVER_INTERACTIVE" /D yylval=pcap_lval /D "_USRDLL" /D "LIBPCAP_EXPORTS" /D "HAVE_STRERROR" /D "_DEBUG" /D "__STDC__" /D "INET6" /D "_WINDOWS" /D "_MBCS" /D SIZEOF_CHAR=1 /D SIZEOF_SHORT=2 /D SIZEOF_INT=4 /D "HAVE_ADDRINFO" /D "WIN32" /D _U_= /YX /FD /GZ /c
 # ADD BASE RSC /l 0x409 /d "_DEBUG"
 # ADD RSC /l 0x409 /d "_DEBUG"
 BSC32=bscmake.exe