diff --git a/include/sect.h b/include/sect.h
index e1f0134d..330271f6 100644
--- a/include/sect.h
+++ b/include/sect.h
@@ -89,12 +89,19 @@ struct sctstr {
     time_t sct_timestamp;	/* Last time this sector was written to */
 };
 
+typedef enum {
+    NAV_NONE,	/* ships can't navigate */
+    NAVOK,	/* ships can always navigate */
+    NAV_02,	/* requires 2% effic to navigate */
+    NAV_60	/* requires 60% effic to navigate */
+} d_navigation;
+
 struct dchrstr {
     unsigned char d_uid;
     int d_mnem;			/* map symbol */
     int d_prd;			/* product type */
     int d_mcst;			/* movement cost */
-    int d_nav;			/* navigation capability */
+    d_navigation d_nav;			/* navigation capability */
     i_packing d_pkg;		/* type of packaging in these sects */
     float d_ostr;		/* offensive strength */
     float d_dstr;		/* defensive strength */
@@ -107,12 +114,6 @@ struct dchrstr {
     char *d_name;		/* full name of sector type */
 };
 
-/* for d_nav */
-#define	NAV_NONE    0		/* ships can't navigate */
-#define	NAVOK	1		/* ships can always navigate */
-#define	NAV_02	2		/* requires 2% effic to navigate */
-#define	NAV_60	3		/* requires 60% effic to navigate */
-
 	/* sector types (must agree with order in dchr, empglb.c) */
 
 #define	SCT_WATER	0	/* basics */
diff --git a/src/lib/global/nsc.c b/src/lib/global/nsc.c
index 3557c67a..057298fc 100644
--- a/src/lib/global/nsc.c
+++ b/src/lib/global/nsc.c
@@ -167,7 +167,7 @@ struct castr dchr_ca[] = {
     {NSC_INT, NSC_CONST, 0, offsetof(struct dchrstr, d_mnem), "mnem", EF_BAD},
     {NSC_INT, 0, 0, offsetof(struct dchrstr, d_prd), "prd", EF_PRODUCT},
     {NSC_INT, 0, 0, offsetof(struct dchrstr, d_mcst), "mcst", EF_BAD},
-    {NSC_INT, 0, 0, offsetof(struct dchrstr, d_nav), "nav",
+    {NSC_SITYPE(d_navigation), 0, 0, offsetof(struct dchrstr, d_nav), "nav",
      EF_SECTOR_NAVIGATION},
     {NSC_SITYPE(i_packing), 0, 0, offsetof(struct dchrstr, d_pkg), "pkg",
      EF_PACKING},