diff --git a/src/lib/commands/echo.c b/src/lib/commands/echo.c
index 6562c6a5..12bfeb59 100644
--- a/src/lib/commands/echo.c
+++ b/src/lib/commands/echo.c
@@ -40,7 +40,7 @@
 int
 echo(void)
 {
-    pr("%s\n", player->argp[1] ? player->argp[1] : (s_char *)"");
+    pr("%s\n", player->argp[1] ? player->argp[1] : "");
 
     return RET_OK;
 }
diff --git a/src/lib/commands/map.c b/src/lib/commands/map.c
index 43cda4b1..b8c98538 100644
--- a/src/lib/commands/map.c
+++ b/src/lib/commands/map.c
@@ -82,7 +82,7 @@ map(void)
 	}
     }
 
-    if (player->argp[1] == (s_char *)0) {
+    if (player->argp[1] == NULL) {
 	if ((str = getstring("(sects)? ", buf)) == 0)
 	    return RET_SYN;
     } else {
diff --git a/src/lib/commands/miss.c b/src/lib/commands/miss.c
index 1bb81edd..7086354e 100644
--- a/src/lib/commands/miss.c
+++ b/src/lib/commands/miss.c
@@ -178,7 +178,7 @@ mission(void)
 	y = 0;
     }
 
-    if (player->argp[5] != (s_char *)0) {
+    if (player->argp[5] != NULL) {
 	desired_radius = atoi(player->argp[5]);
 	if (desired_radius < 0) {
 	    pr("Radius must be greater than zero!\n");
diff --git a/src/lib/commands/retr.c b/src/lib/commands/retr.c
index 3e8f30e5..78d867b4 100644
--- a/src/lib/commands/retr.c
+++ b/src/lib/commands/retr.c
@@ -61,10 +61,10 @@ retr(void)
     if (!snxtitem(&ni, EF_SHIP, player->argp[1]))
 	return RET_SYN;
     nships = 0;
-    if (player->argp[1] != (s_char *)0)
+    if (player->argp[1] != NULL)
 	if (isalpha(player->argp[1][0]))
 	    isfleet = RET_GROUP;
-    if (player->argp[2] != (s_char *)0)
+    if (player->argp[2] != NULL)
 	pq = getstarg(player->argp[2], "Retreat path? ", buf1);
     else
 	pq = (s_char *)0;
@@ -209,10 +209,10 @@ lretr(void)
     if (!snxtitem(&ni, EF_LAND, player->argp[1]))
 	return RET_SYN;
     nunits = 0;
-    if (player->argp[1] != (s_char *)0)
+    if (player->argp[1] != NULL)
 	if (isalpha(player->argp[1][0]))
 	    isarmy = RET_GROUP;
-    if (player->argp[2] != (s_char *)0)
+    if (player->argp[2] != NULL)
 	pq = getstarg(player->argp[2], "Retreat path? ", buf1);
     else
 	pq = (s_char *)0;
diff --git a/src/lib/commands/rout.c b/src/lib/commands/rout.c
index 7a9628fc..65581cc2 100644
--- a/src/lib/commands/rout.c
+++ b/src/lib/commands/rout.c
@@ -75,7 +75,7 @@ rout(void)
     if ((ip = whatitem(player->argp[1], "What item? ")) == 0)
 	return RET_SYN;
     i_del = ip->i_vtype;;
-    if (player->argp[2] == (s_char *)0) {
+    if (player->argp[2] == NULL) {
 	if ((str = getstring("(sects)? ", buf1)) == 0)
 	    return RET_SYN;
     } else {
diff --git a/src/lib/commands/sect.c b/src/lib/commands/sect.c
index 90435bcb..70cc5a5a 100644
--- a/src/lib/commands/sect.c
+++ b/src/lib/commands/sect.c
@@ -66,7 +66,7 @@ sct(void)
     static s_char **map = (s_char **)0;
 
     nsect = 0;
-    if (player->argp[1] == (s_char *)0) {
+    if (player->argp[1] == NULL) {
 	if ((str = getstring("(sects)? ", buf)) == 0)
 	    return RET_SYN;
     } else {
diff --git a/src/lib/commands/surv.c b/src/lib/commands/surv.c
index 29222ab4..67f6f318 100644
--- a/src/lib/commands/surv.c
+++ b/src/lib/commands/surv.c
@@ -86,7 +86,7 @@ surv(void)
     for (; isspace(*ptr); ++ptr) ;
     if (*ptr)
 	return RET_SYN;
-    if (player->argp[2] == (s_char *)0) {
+    if (player->argp[2] == NULL) {
 	if ((str = getstring("(sects)? ", buf)) == 0)
 	    return RET_SYN;
     } else {
diff --git a/src/lib/commands/tele.c b/src/lib/commands/tele.c
index aba4ac10..93d21c06 100644
--- a/src/lib/commands/tele.c
+++ b/src/lib/commands/tele.c
@@ -73,7 +73,7 @@ tele(void)
 	int kk;
 
 	kk = 1;
-	while (player->argp[kk] != (s_char *)0) {
+	while (player->argp[kk] != NULL) {
 	    if ((n = natarg(player->argp[kk], "for which country? ")) < 0) {
 		if (opt_HIDDEN) {
 		    if (n < -1) {
diff --git a/src/lib/subs/attsub.c b/src/lib/subs/attsub.c
index a9a6eaab..f1eb6e7f 100644
--- a/src/lib/subs/attsub.c
+++ b/src/lib/subs/attsub.c
@@ -706,10 +706,10 @@ att_ask_support(int offset, int *fortp, int *shipp, int *landp,
     s_char *p;
     *fortp = *shipp = *landp = *planep = 1;
 
-    if (player->argp[offset] != (s_char *)0) {
-	if ((player->argp[offset + 1] == (s_char *)0) ||
-	    (player->argp[offset + 2] == (s_char *)0) ||
-	    (player->argp[offset + 3] == (s_char *)0)) {
+    if (player->argp[offset] != NULL) {
+	if ((player->argp[offset + 1] == NULL) ||
+	    (player->argp[offset + 2] == NULL) ||
+	    (player->argp[offset + 3] == NULL)) {
 	    pr("If any support arguments are used, all must be!\n");
 	    return RET_SYN;
 	}