diff --git a/src/main/java/com/google/devtools/build/lib/runtime/BlazeOptionHandler.java b/src/main/java/com/google/devtools/build/lib/runtime/BlazeOptionHandler.java
index 9287d53..31b3ebc 100644
--- a/src/main/java/com/google/devtools/build/lib/runtime/BlazeOptionHandler.java
+++ b/src/main/java/com/google/devtools/build/lib/runtime/BlazeOptionHandler.java
@@ -110,7 +110,10 @@
           Event.error(
               "The '"
                   + commandAnnotation.name()
-                  + "' command is only supported from within a workspace."));
+                  + "' command is only supported from within a workspace"
+                  + " (below a directory having a WORKSPACE file).\n"
+                  + "See documentation at"
+                  + " https://docs.bazel.build/versions/master/build-ref.html#workspace"));
       return ExitCode.COMMAND_LINE_ERROR;
     }