diff --git a/flang/tools/f18/flang b/flang/tools/f18/flang
--- a/flang/tools/f18/flang
+++ b/flang/tools/f18/flang
@@ -358,6 +358,12 @@
   # first generated and then deleted by this script.
   # NOTE: We need to make sure that the base-name is unique to every
   # invocation. Otherwise we can't use this script in parallel.
+  if ! command -v uuidgen &> /dev/null
+  then
+    echo "uuidgen is required for generating unparsed file names."
+    exit 1
+  fi
+
   local -r unique_id=$(uuidgen | cut -b25-36)
   local -r unparsed_file_base="flang_unparsed_file_$unique_id"