diff --git a/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp b/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
index 7bc522154906..fa165cf2d402 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
@@ -811,12 +811,19 @@ DWARFUnit::determineStringOffsetsTableContribution(DWARFDataExtractor &DA) {
   auto Offset = toSectionOffset(getUnitDIE().find(DW_AT_str_offsets_base), 0);
   Optional<StrOffsetsContributionDescriptor> Descriptor;
   // Attempt to find a DWARF64 contribution 16 bytes before the base.
-  if (Offset >= 16)
+  switch (Header.getFormat()) {
+  case dwarf::DwarfFormat::DWARF64:
+    if (Offset < 16)
+      return None;
     Descriptor =
         parseDWARF64StringOffsetsTableHeader(DA, (uint32_t)Offset - 16);
-  // Try to find a DWARF32 contribution 8 bytes before the base.
-  if (!Descriptor && Offset >= 8)
+    break;
+  case dwarf::DwarfFormat::DWARF32:
+    if (Offset < 8)
+      return None;
     Descriptor = parseDWARF32StringOffsetsTableHeader(DA, (uint32_t)Offset - 8);
+    break;
+  }
   return Descriptor ? Descriptor->validateContributionSize(DA) : Descriptor;
 }
 
diff --git a/llvm/test/DebugInfo/X86/dwarfdump-str-offsets-macho.s b/llvm/test/DebugInfo/X86/dwarfdump-str-offsets-macho.s
index 1332a94ec3c7..10a810a350d1 100644
--- a/llvm/test/DebugInfo/X86/dwarfdump-str-offsets-macho.s
+++ b/llvm/test/DebugInfo/X86/dwarfdump-str-offsets-macho.s
@@ -160,18 +160,19 @@ CU1_5_version:
 CU1_5_end:
 
 # DWARF v5 CU header
-        .long  CU2_5_end-CU2_5_version  # Length of Unit
+        .long  0xffffffff
+        .quad  CU2_5_end-CU2_5_version  # Length of Unit
 CU2_5_version:
         .short 5               # DWARF version number
         .byte 1                # DWARF Unit Type
         .byte 8                # Address Size (in bytes)
-        .long 0                # Offset Into Abbrev. Section
+        .quad 0                # Offset Into Abbrev. Section
 # The compile-unit DIE, which has a DW_AT_producer, DW_AT_name,
 # DW_AT_str_offsets and DW_AT_compdir.
         .byte 1                # Abbreviation code
         .byte 0                # The index of the producer string
         .byte 1                # The index of the CU name string
-        .long Ldebug_str_offsets_base1-Ldebug_str_offsets
+        .quad Ldebug_str_offsets_base1-Ldebug_str_offsets
         .byte 2                # The index of the comp dir string
         .byte 0 # NULL
 CU2_5_end: