diff -r 02ea468ecf07 -r f817692c929f src/Pure/System/isabelle_system.scala
--- a/src/Pure/System/isabelle_system.scala	Tue Mar 16 22:13:04 2021 +0100
+++ b/src/Pure/System/isabelle_system.scala	Tue Mar 16 23:30:51 2021 +0100
@@ -491,7 +491,7 @@
   def require_command(cmds: String*): Unit =
   {
     for (cmd <- cmds) {
-      if (!bash(Bash.string(cmd) + " --version").ok) error("Missing command: " + quote(cmd))
+      if (!bash(Bash.string(cmd) + " --version").ok) error("Missing system command: " + quote(cmd))
     }
   }