Index: head/bin/sh/parser.c
===================================================================
--- head/bin/sh/parser.c
+++ head/bin/sh/parser.c
@@ -2014,8 +2014,9 @@
 				gethostname(&ps[i], PROMPTLEN - i);
 				/* Skip to end of hostname. */
 				trim = (*fmt == 'h') ? '.' : '\0';
-				while ((ps[i+1] != '\0') && (ps[i+1] != trim))
+				while ((ps[i] != '\0') && (ps[i] != trim))
 					i++;
+				--i;
 				break;
 
 				/*
@@ -2027,7 +2028,7 @@
 			case 'W':
 			case 'w':
 				pwd = lookupvar("PWD");
-				if (pwd == NULL)
+				if (pwd == NULL || *pwd == '\0')
 					pwd = "?";
 				if (*fmt == 'W' &&
 				    *pwd == '/' && pwd[1] != '\0')