diff --git a/scripts/kconfig/lexer.l b/scripts/kconfig/lexer.l
index 240109f965ae..72e5e9ac52bb 100644
--- a/scripts/kconfig/lexer.l
+++ b/scripts/kconfig/lexer.l
@@ -305,8 +305,11 @@ static char *expand_token(const char *in, size_t n)
 	new_string();
 	append_string(in, n);
 
-	/* get the whole line because we do not know the end of token. */
-	while ((c = input()) != EOF) {
+	/*
+	 * get the whole line because we do not know the end of token.
+	 * input() returns 0 (not EOF!) when it reachs the end of file.
+	 */
+	while ((c = input()) != 0) {
 		if (c == '\n') {
 			unput(c);
 			break;