diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 4def44cd776..1e12b39a978 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -2539,6 +2539,8 @@ void DwarfDebug::emitDebugLocDWO() {
       Asm->emitInt8(dwarf::DW_LLE_startx_length);
       unsigned idx = AddrPool.getIndex(Entry.Begin);
       Asm->EmitULEB128(idx);
+      // Also the pre-standard encoding is slightly different, emitting this as
+      // an address-length entry here, but its a ULEB128 in DWARFv5 loclists.
       Asm->EmitLabelDifference(Entry.End, Entry.Begin, 4);
       emitDebugLocEntryLocation(Entry, List.CU);
     }