diff --git a/lib/isc/lex.c b/lib/isc/lex.c

index cd44fe3..5b7c539 100644

--- a/lib/isc/lex.c

+++ b/lib/isc/lex.c

@@ -27,6 +27,8 @@

 #include <isc/string.h>

 #include <isc/util.h>

+#include "../errno2result.h"

+

 typedef struct inputsource {

 	isc_result_t result;

 	bool is_file;

@@ -422,7 +424,7 @@ isc_lex_gettoken(isc_lex_t *lex, unsigned int options, isc_token_t *tokenp) {

 #endif /* if defined(HAVE_FLOCKFILE) && defined(HAVE_GETC_UNLOCKED) */

 				if (c == EOF) {

 					if (ferror(stream)) {

-						source->result = ISC_R_IOERROR;

+						source->result = isc__errno2result(errno);

 						result = source->result;

 						goto done;

 					}

diff --git a/lib/isc/unix/errno2result.c b/lib/isc/unix/errno2result.c

index e3e2644..5e58600 100644

--- a/lib/isc/unix/errno2result.c

+++ b/lib/isc/unix/errno2result.c

@@ -37,6 +37,7 @@ isc___errno2result(int posixerrno, bool dolog, const char *file,

 	case EINVAL: /* XXX sometimes this is not for files */

 	case ENAMETOOLONG:

 	case EBADF:

+	case EISDIR:

 		return (ISC_R_INVALIDFILE);

 	case ENOENT:

 		return (ISC_R_FILENOTFOUND);