diff --git a/llvm/include/llvm/CodeGen/MachineInstrBuilder.h b/llvm/include/llvm/CodeGen/MachineInstrBuilder.h
index a5b8d3af3cc9b..0a73b0f6b3673 100644
--- a/llvm/include/llvm/CodeGen/MachineInstrBuilder.h
+++ b/llvm/include/llvm/CodeGen/MachineInstrBuilder.h
@@ -40,6 +40,7 @@ class MDNode;
 
 namespace RegState {
 
+// Keep this in sync with the table in MIRLangRef.rst.
 enum {
   /// Register definition.
   Define = 0x2,