diff --git a/lib/isc/errno2result.c b/lib/isc/errno2result.c
index 623ac6dbe9..0c465952be 100644
--- a/lib/isc/errno2result.c
+++ b/lib/isc/errno2result.c
@@ -37,6 +37,8 @@ isc___errno2result(int posixerrno, bool dolog, const char *file,
 	case ENAMETOOLONG:
 	case EBADF:
 		return (ISC_R_INVALIDFILE);
+	case EISDIR:
+		return (ISC_R_NOTFILE);
 	case ENOENT:
 		return (ISC_R_FILENOTFOUND);
 	case EACCES:
diff --git a/lib/isc/lex.c b/lib/isc/lex.c
index 8ab3682873..b09c09635a 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;
@@ -425,7 +427,9 @@ 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;
 					}