diff --git a/libpcap/Makefile.in b/libpcap/Makefile.in
index c12b93bc3..5bdececd3 100644
--- a/libpcap/Makefile.in
+++ b/libpcap/Makefile.in
@@ -303,6 +303,15 @@ EXTRA_DIST = \
 	Win32/Src/inet_net.c \
 	Win32/Src/inet_pton.c
 
+# Inihibit implicit rule Make seems to have for using yacc/lex to
+# recompile new scanner.c/grammar.c -- we ship ones which we want to
+# use instead.
+grammar.c:
+	echo "Not rebuilding grammar.c or scanner.c"
+
+scanner.c:
+	echo "Not rebuilding grammar.c or scanner.c"
+
 all: libpcap.a pcap-config
 
 libpcap.a: $(OBJ)
@@ -320,6 +329,9 @@ libpcap.so: $(OBJ)
 	@rm -f $@
 	$(CC) -shared -Wl,-soname,$@.1 -o $@.`cat $(srcdir)/VERSION` $(OBJ) $(DAGLIBS)
 
+grammar.c scanner.c:
+	echo
+
 #
 # The following rule succeeds, but the result is untested.
 #
diff --git a/libpcap/NMAP_MODIFICATIONS b/libpcap/NMAP_MODIFICATIONS
index 05e2a2ef7..d8ead1618 100644
--- a/libpcap/NMAP_MODIFICATIONS
+++ b/libpcap/NMAP_MODIFICATIONS
@@ -1,5 +1,39 @@
 o Included this file, renamed directory from libpcap-1.0.0 to libpcap.
 
+o Added dummy rules to inhibit GNU Make's implicit yacc/lex creation
+  of scanner.c and grammar.c:
+Index: Makefile.in
+===================================================================
+--- Makefile.in	(revision 15981)
++++ Makefile.in	(working copy)
+@@ -303,6 +303,15 @@
+ 	Win32/Src/inet_net.c \
+ 	Win32/Src/inet_pton.c
+ 
++# Inihibit implicit rule Make seems to have for using yacc/lex to
++# recompile new scanner.c/grammar.c -- we ship ones which we want to
++# use instead.
++grammar.c:
++	echo "Not rebuilding grammar.c or scanner.c"
++
++scanner.c:
++	echo "Not rebuilding grammar.c or scanner.c"
++
+ all: libpcap.a pcap-config
+ 
+ libpcap.a: $(OBJ)
+@@ -320,6 +329,9 @@
+ 	@rm -f $@
+ 	$(CC) -shared -Wl,-soname,$@.1 -o $@.`cat $(srcdir)/VERSION` $(OBJ) $(DAGLIBS)
+ 
++grammar.c scanner.c:
++	echo
++
+ #
+ # The following rule succeeds, but the result is untested.
+ #
+
+
 o Removed these files and directories:
   packaging/
   config.guess