diff --git a/doc/bison.texi b/doc/bison.texi
index aeca17a6..89e2673a 100644
--- a/doc/bison.texi
+++ b/doc/bison.texi
@@ -11649,6 +11649,18 @@ then the parser's to get the set of defined tokens.
 #  pragma GCC diagnostic ignored "-Wregister"
 # endif
 #endif
+
+#if FLEX_VERSION < 206
+# if defined __clang__
+#  pragma clang diagnostic ignored "-Wconversion"
+#  pragma clang diagnostic ignored "-Wdocumentation"
+#  pragma clang diagnostic ignored "-Wshorten-64-to-32"
+#  pragma clang diagnostic ignored "-Wsign-conversion"
+# elif defined __GNUC__
+#  pragma GCC diagnostic ignored "-Wconversion"
+#  pragma GCC diagnostic ignored "-Wsign-conversion"
+# endif
+#endif
 %@}
 @end example
 @end ignore