diff --git a/flang/tools/f18/flang b/flang/tools/f18/flang
--- a/flang/tools/f18/flang
+++ b/flang/tools/f18/flang
@@ -12,6 +12,8 @@
 #   * run Flang's compiler driver to unparse the input source files
 #   * use the external compiler (defined via FLANG_FC environment variable) to
 #   compile the unparsed source files
+#
+# Tested with Bash 4.4.23 (please use Bash >= 4.4.23 to run it).
 #===------------------------------------------------------------------------===#
 set -euo pipefail