diff --git a/sys/fs/msdosfs/msdosfs_vnops.c b/sys/fs/msdosfs/msdosfs_vnops.c
--- a/sys/fs/msdosfs/msdosfs_vnops.c
+++ b/sys/fs/msdosfs/msdosfs_vnops.c
@@ -1944,6 +1944,9 @@
 	case _PC_HAS_HIDDENSYSTEM:
 		*ap->a_retval = 1;
 		return (0);
+	case _PC_CASE_INSENSITIVE:
+		*ap->a_retval = 1;
+		return (0);
 	default:
 		return (vop_stdpathconf(ap));
 	}
diff --git a/sys/kern/vfs_default.c b/sys/kern/vfs_default.c
--- a/sys/kern/vfs_default.c
+++ b/sys/kern/vfs_default.c
@@ -458,6 +458,7 @@
 		case _PC_HAS_NAMEDATTR:
 		case _PC_HAS_HIDDENSYSTEM:
 		case _PC_CLONE_BLKSIZE:
+		case _PC_CASE_INSENSITIVE:
 			*ap->a_retval = 0;
 			return (0);
 		default:
diff --git a/sys/sys/unistd.h b/sys/sys/unistd.h
--- a/sys/sys/unistd.h
+++ b/sys/sys/unistd.h
@@ -160,6 +160,7 @@
 #define	_PC_XATTR_EXISTS	_PC_HAS_NAMEDATTR	/* Solaris Compatible */
 #define	_PC_HAS_HIDDENSYSTEM	68
 #define	_PC_CLONE_BLKSIZE	69
+#define	_PC_CASE_INSENSITIVE	70
 #endif
 
 /* From OpenSolaris, used by SEEK_DATA/SEEK_HOLE. */