diff --git a/cmd/lefty/dot2l/dotlex.c b/cmd/lefty/dot2l/dotlex.c

index cf738c0..65e17e2 100644

--- a/cmd/lefty/dot2l/dotlex.c

+++ b/cmd/lefty/dot2l/dotlex.c

@@ -252,7 +252,7 @@ static char *scan_token (char *p) {

     char *q;

     q = lexbuf;

-    if (p == '\0')

+    if (!p || *p == '\0')

         return NULL;

     while (isalnum (*p) || (*p == '_') || (!isascii (*p)))

         *q++ = *p++;

diff --git a/cmd/tools/gvgen.c b/cmd/tools/gvgen.c

index c2b166d..c9a51e9 100644

--- a/cmd/tools/gvgen.c

+++ b/cmd/tools/gvgen.c

@@ -453,6 +453,8 @@ closeOpen (void)

 	fprintf(opts.outfile, "}\ngraph {\n");

 }

+extern void makeTetrix(int depth, edgefn ef);

+

 int main(int argc, char *argv[])

 {

     GraphType graphType;