diff --git a/test/lit.cfg.py b/test/lit.cfg.py
index 46de5c18a..2d5d30e0a 100644
--- a/test/lit.cfg.py
+++ b/test/lit.cfg.py
@@ -75,6 +75,8 @@
     config.available_features.add('spirv-link')
     using_spirv_tools = True
 
+# Unlike spirv-{as,dis,link} above, running spirv-val is optional: if spirv-val is
+# not available, the test must still run and just skip any spirv-val commands.
 if config.spirv_tools_have_spirv_val:
     llvm_config.add_tool_substitutions(['spirv-val'], [config.spirv_tools_bin_dir])
     using_spirv_tools = True