Index: vfontedpr.c
--- vfontedpr.c.orig
+++ vfontedpr.c
@@ -233,7 +233,7 @@ main(int argc, char *argv[])
 	    cpp = l_keywds;
 	    while (*cp) {
 		while (*cp == ' ' || *cp =='\t')
-		    *cp++ = NULL;
+		    *cp++ = '\0';
 		if (*cp)
 		    *cpp++ = cp;
 		while (*cp != ' ' && *cp  != '\t' && *cp)
@@ -275,7 +275,7 @@ main(int argc, char *argv[])
 	x_escaped = FALSE;
 	blklevel = 0;
 	for (psptr=0; psptr<PSMAX; psptr++) {
-	    pstack[psptr][0] = NULL;
+	    pstack[psptr][0] = '\0';
 	    plstack[psptr] = 0;
 	}
 	psptr = -1;
@@ -358,7 +358,7 @@ putScp(char *os)
 	if (psptr < PSMAX) {
 	    ++psptr;
 	    strncpy (pstack[psptr], pname, PNAMELEN);
-	    pstack[psptr][PNAMELEN] = NULL;
+	    pstack[psptr][PNAMELEN] = '\0';
 	    plstack[psptr] = blklevel;
 	}
     } 
@@ -656,7 +656,7 @@ putcp(int c)
 static boolean
 isproc(char *s)
 {
-    pname[0] = NULL;
+    pname[0] = '\0';
     if (!l_toplex || blklevel == 0)
 	if (expmatch (s, l_prcbeg, pname) != NIL) {
 	    return (TRUE);