diff --git a/scripts/kconfig/symbol.c b/scripts/kconfig/symbol.c
index c0efe102d655c40547afe92014cec1c74b70b3c2..af6e9f3de9503b033a69a3eba7c2ecd212fef747 100644
--- a/scripts/kconfig/symbol.c
+++ b/scripts/kconfig/symbol.c
@@ -875,7 +875,7 @@ const char *sym_expand_string_value(const char *in)
 			symval = sym_get_string_value(sym);
 		}
 
-		newlen = strlen(res) + strlen(symval) + strlen(src);
+		newlen = strlen(res) + strlen(symval) + strlen(src) + 1;
 		if (newlen > reslen) {
 			reslen = newlen;
 			res = realloc(res, reslen);