diff --git a/llvm/lib/DebugInfo/DWARF/DWARFAcceleratorTable.cpp b/llvm/lib/DebugInfo/DWARF/DWARFAcceleratorTable.cpp
--- a/llvm/lib/DebugInfo/DWARF/DWARFAcceleratorTable.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFAcceleratorTable.cpp
@@ -365,6 +365,7 @@
 void DWARFDebugNames::Header::dump(ScopedPrinter &W) const {
   DictScope HeaderScope(W, "Header");
   W.printHex("Length", UnitLength);
+  W.printString("Format", dwarf::FormatString(Format));
   W.printNumber("Version", Version);
   W.printNumber("CU count", CompUnitCount);
   W.printNumber("Local TU count", LocalTypeUnitCount);
diff --git a/llvm/test/DebugInfo/X86/dwarfdump-debug-names.s b/llvm/test/DebugInfo/X86/dwarfdump-debug-names.s
--- a/llvm/test/DebugInfo/X86/dwarfdump-debug-names.s
+++ b/llvm/test/DebugInfo/X86/dwarfdump-debug-names.s
@@ -137,6 +137,7 @@
 # CHECK-NEXT: Name Index @ 0x0 {
 # CHECK-NEXT:   Header {
 # CHECK-NEXT:     Length: 0x60
+# CHECK-NEXT:     Format: DWARF32
 # CHECK-NEXT:     Version: 5
 # CHECK-NEXT:     CU count: 1
 # CHECK-NEXT:     Local TU count: 0
@@ -182,6 +183,7 @@
 # CHECK-NEXT: Name Index @ 0x64 {
 # CHECK-NEXT:   Header {
 # CHECK-NEXT:     Length: 0x44
+# CHECK-NEXT:     Format: DWARF32
 # CHECK-NEXT:     Version: 5
 # CHECK-NEXT:     CU count: 1
 # CHECK-NEXT:     Local TU count: 0
@@ -215,6 +217,7 @@
 # CHECK-NEXT: Name Index @ 0xac {
 # CHECK-NEXT:   Header {
 # CHECK-NEXT:     Length: 0x68
+# CHECK-NEXT:     Format: DWARF64
 # CHECK-NEXT:     Version: 5
 # CHECK-NEXT:     CU count: 1
 # CHECK-NEXT:     Local TU count: 1