diff --git a/llvm/lib/ObjectYAML/CodeViewYAMLSymbols.cpp b/llvm/lib/ObjectYAML/CodeViewYAMLSymbols.cpp
index 724ddc1c07d4..b7f9bde96193 100644
--- a/llvm/lib/ObjectYAML/CodeViewYAMLSymbols.cpp
+++ b/llvm/lib/ObjectYAML/CodeViewYAMLSymbols.cpp
@@ -81,6 +81,7 @@ void ScalarEnumerationTraits<SymbolKind>::enumeration(IO &io,
   auto SymbolNames = getSymbolTypeNames();
   for (const auto &E : SymbolNames)
     io.enumCase(Value, E.Name, E.Value);
+  io.enumFallback<yaml::Hex16>(Value);
 }
 
 void ScalarBitSetTraits<CompileSym2Flags>::bitset(IO &io,
diff --git a/llvm/lib/ObjectYAML/CodeViewYAMLTypes.cpp b/llvm/lib/ObjectYAML/CodeViewYAMLTypes.cpp
index 29b5989feb99..1542017d9d7e 100644
--- a/llvm/lib/ObjectYAML/CodeViewYAMLTypes.cpp
+++ b/llvm/lib/ObjectYAML/CodeViewYAMLTypes.cpp
@@ -24,6 +24,7 @@
 #include "llvm/DebugInfo/CodeView/TypeDeserializer.h"
 #include "llvm/DebugInfo/CodeView/TypeIndex.h"
 #include "llvm/DebugInfo/CodeView/TypeVisitorCallbacks.h"
+#include "llvm/ObjectYAML/YAML.h"
 #include "llvm/Support/Allocator.h"
 #include "llvm/Support/BinaryStreamReader.h"
 #include "llvm/Support/BinaryStreamWriter.h"
@@ -86,6 +87,31 @@ struct LeafRecordBase {
   virtual Error fromCodeViewRecord(CVType Type) = 0;
 };
 
+struct UnknownLeafRecord : public LeafRecordBase {
+  explicit UnknownLeafRecord(TypeLeafKind K) : LeafRecordBase(K) {}
+
+  void map(yaml::IO &IO) override;
+
+  CVType toCodeViewRecord(AppendingTypeTableBuilder &TS) const override {
+    RecordPrefix Prefix;
+    uint32_t TotalLen = sizeof(RecordPrefix) + Data.size();
+    Prefix.RecordKind = Kind;
+    Prefix.RecordLen = TotalLen - 2;
+    uint8_t *Buffer = TS.getAllocator().Allocate<uint8_t>(TotalLen);
+    ::memcpy(Buffer, &Prefix, sizeof(RecordPrefix));
+    ::memcpy(Buffer + sizeof(RecordPrefix), Data.data(), Data.size());
+    return CVType(ArrayRef<uint8_t>(Buffer, TotalLen));
+  }
+
+  Error fromCodeViewRecord(CVType Type) override {
+    this->Kind = Type.kind();
+    Data = Type.content();
+    return Error::success();
+  }
+
+  std::vector<uint8_t> Data;
+};
+
 template <typename T> struct LeafRecordImpl : public LeafRecordBase {
   explicit LeafRecordImpl(TypeLeafKind K)
       : LeafRecordBase(K), Record(static_cast<TypeRecordKind>(K)) {}
@@ -200,6 +226,7 @@ void ScalarEnumerationTraits<TypeLeafKind>::enumeration(IO &io,
 #define CV_TYPE(name, val) io.enumCase(Value, #name, name);
 #include "llvm/DebugInfo/CodeView/CodeViewTypes.def"
 #undef CV_TYPE
+  io.enumFallback<Hex16>(Value);
 }
 
 void ScalarEnumerationTraits<PointerToMemberRepresentation>::enumeration(
@@ -397,6 +424,19 @@ namespace llvm {
 namespace CodeViewYAML {
 namespace detail {
 
+void UnknownLeafRecord::map(IO &IO) {
+  yaml::BinaryRef Binary;
+  if (IO.outputting())
+    Binary = yaml::BinaryRef(Data);
+  IO.mapRequired("Data", Binary);
+  if (!IO.outputting()) {
+    std::string Str;
+    raw_string_ostream OS(Str);
+    Binary.writeAsBinary(OS);
+    Data.assign(Str.begin(), Str.end());
+  }
+}
+
 template <> void LeafRecordImpl<ModifierRecord>::map(IO &IO) {
   IO.mapRequired("ModifiedType", Record.ModifiedType);
   IO.mapRequired("Modifiers", Record.Modifiers);
@@ -678,7 +718,7 @@ template <typename T>
 static inline Expected<LeafRecord> fromCodeViewRecordImpl(CVType Type) {
   LeafRecord Result;
 
-  auto Impl = std::make_shared<LeafRecordImpl<T>>(Type.kind());
+  auto Impl = std::make_shared<T>(Type.kind());
   if (auto EC = Impl->fromCodeViewRecord(Type))
     return std::move(EC);
   Result.Leaf = std::move(Impl);
@@ -688,7 +728,7 @@ static inline Expected<LeafRecord> fromCodeViewRecordImpl(CVType Type) {
 Expected<LeafRecord> LeafRecord::fromCodeViewRecord(CVType Type) {
 #define TYPE_RECORD(EnumName, EnumVal, ClassName)                              \
   case EnumName:                                                               \
-    return fromCodeViewRecordImpl<ClassName##Record>(Type);
+    return fromCodeViewRecordImpl<LeafRecordImpl<ClassName##Record>>(Type);
 #define TYPE_RECORD_ALIAS(EnumName, EnumVal, AliasName, ClassName)             \
   TYPE_RECORD(EnumName, EnumVal, ClassName)
 #define MEMBER_RECORD(EnumName, EnumVal, ClassName)
@@ -696,9 +736,8 @@ Expected<LeafRecord> LeafRecord::fromCodeViewRecord(CVType Type) {
   switch (Type.kind()) {
 #include "llvm/DebugInfo/CodeView/CodeViewTypes.def"
   default:
-      llvm_unreachable("Unknown leaf kind!");
+    return fromCodeViewRecordImpl<UnknownLeafRecord>(Type);
   }
-  return make_error<CodeViewError>(cv_error_code::corrupt_record);
 }
 
 CVType
@@ -724,7 +763,7 @@ template <typename ConcreteType>
 static void mapLeafRecordImpl(IO &IO, const char *Class, TypeLeafKind Kind,
                               LeafRecord &Obj) {
   if (!IO.outputting())
-    Obj.Leaf = std::make_shared<LeafRecordImpl<ConcreteType>>(Kind);
+    Obj.Leaf = std::make_shared<ConcreteType>(Kind);
 
   if (Kind == LF_FIELDLIST)
     Obj.Leaf->map(IO);
@@ -740,7 +779,8 @@ void MappingTraits<LeafRecord>::mapping(IO &IO, LeafRecord &Obj) {
 
 #define TYPE_RECORD(EnumName, EnumVal, ClassName)                              \
   case EnumName:                                                               \
-    mapLeafRecordImpl<ClassName##Record>(IO, #ClassName, Kind, Obj);           \
+    mapLeafRecordImpl<LeafRecordImpl<ClassName##Record>>(IO, #ClassName, Kind, \
+                                                         Obj);                 \
     break;
 #define TYPE_RECORD_ALIAS(EnumName, EnumVal, AliasName, ClassName)             \
   TYPE_RECORD(EnumName, EnumVal, ClassName)
@@ -748,7 +788,8 @@ void MappingTraits<LeafRecord>::mapping(IO &IO, LeafRecord &Obj) {
 #define MEMBER_RECORD_ALIAS(EnumName, EnumVal, AliasName, ClassName)
   switch (Kind) {
 #include "llvm/DebugInfo/CodeView/CodeViewTypes.def"
-  default: { llvm_unreachable("Unknown leaf kind!"); }
+  default:
+    mapLeafRecordImpl<UnknownLeafRecord>(IO, "UnknownLeaf", Kind, Obj);
   }
 }
 
diff --git a/llvm/test/tools/llvm-pdbutil/unknown-symbols.test b/llvm/test/tools/llvm-pdbutil/unknown-symbols.test
new file mode 100644
index 000000000000..69d34ae14b44
--- /dev/null
+++ b/llvm/test/tools/llvm-pdbutil/unknown-symbols.test
@@ -0,0 +1,50 @@
+# RUN: llvm-pdbutil yaml2pdb %s --pdb=%t.pdb
+# RUN: llvm-pdbutil dump --symbols %t.pdb | FileCheck --check-prefix=CHECK-YAML2PDB %s
+# RUN: llvm-pdbutil dump --symbols --sym-data %t.pdb | FileCheck --check-prefix=CHECK-YAML2PDB,CHECK-YAML2PDB-SYMDATA %s
+
+# RUN: llvm-pdbutil pdb2yaml --module-syms %t.pdb > %t.yaml
+# RUN: FileCheck --input-file=%t.yaml --check-prefix=CHECK-PDB2YAML %s
+
+# CHECK-YAML2PDB:                                   Symbols
+# CHECK-YAML2PDB:         ============================================================
+# CHECK-YAML2PDB:           Mod 0000 | `F:\Dev\testing\test.obj`:
+# CHECK-YAML2PDB:                4 | S_OBJNAME [size = 32] sig=0, `F:\Dev\testing\test.obj`
+# CHECK-YAML2PDB-SYMDATA:            bytes (
+# CHECK-YAML2PDB-SYMDATA:              0000: 00000000 463A5C44 65765C74 65737469 6E675C74 6573742E 6F626A00           |....F:\Dev\testing\test.obj.|
+# CHECK-YAML2PDB-SYMDATA:            )
+# CHECK-YAML2PDB:               36 | unknown (64188) [size = 36]
+# CHECK-YAML2PDB:                    bytes (
+# CHECK-YAML2PDB:                      0000: 20000000 12100000 00000000 4F015F5F 636F726F 5F667261 6D655F70 74720000  | ...........O.__coro_frame_ptr..|
+# CHECK-YAML2PDB:                    )
+
+# CHECK-PDB2YAML: DbiStream:
+# CHECK-PDB2YAML:   Modules:
+# CHECK-PDB2YAML:     - Module:          'F:\Dev\testing\test.obj'
+# CHECK-PDB2YAML:       ObjFile:         'F:\Dev\testing\test.obj'
+# CHECK-PDB2YAML:       Modi:
+# CHECK-PDB2YAML:         Signature:       4
+# CHECK-PDB2YAML:         Records:
+# CHECK-PDB2YAML:           - Kind:            S_OBJNAME
+# CHECK-PDB2YAML:             ObjNameSym:
+# CHECK-PDB2YAML:               Signature:       0
+# CHECK-PDB2YAML:               ObjectName:      'F:\Dev\testing\test.obj'
+# CHECK-PDB2YAML:           - Kind:            0xFABC
+# CHECK-PDB2YAML:             UnknownSym:
+# CHECK-PDB2YAML:               Data:            2000000012100000000000004F015F5F636F726F5F6672616D655F7074720000
+
+---
+DbiStream:
+  Modules:
+    - Module:          'F:\Dev\testing\test.obj'
+      ObjFile:         'F:\Dev\testing\test.obj'
+      Modi:
+        Signature:       4
+        Records:
+          - Kind:            S_OBJNAME
+            ObjNameSym:
+              Signature:       0
+              ObjectName:      'F:\Dev\testing\test.obj'
+          - Kind:            0xFABC
+            UnknownSym:
+              Data:            2000000012100000000000004F015F5F636F726F5F6672616D655F7074720000
+...
diff --git a/llvm/test/tools/llvm-pdbutil/unknown-types.test b/llvm/test/tools/llvm-pdbutil/unknown-types.test
new file mode 100644
index 000000000000..7d5a7b43e982
--- /dev/null
+++ b/llvm/test/tools/llvm-pdbutil/unknown-types.test
@@ -0,0 +1,41 @@
+# RUN: llvm-pdbutil yaml2pdb %s --pdb=%t.pdb
+# RUN: llvm-pdbutil dump --types %t.pdb | FileCheck --check-prefix=CHECK-YAML2PDB %s
+# RUN: llvm-pdbutil dump --types --type-data %t.pdb | FileCheck --check-prefix=CHECK-YAML2PDB,CHECK-YAML2PDB-TYPE-DATA %s
+
+# RUN: llvm-pdbutil pdb2yaml --tpi-stream %t.pdb > %t.yaml
+# RUN: FileCheck --input-file=%t.yaml --check-prefix=CHECK-PDB2YAML %s
+
+# CHECK-YAML2PDB:                                Types (TPI Stream)
+# CHECK-YAML2PDB:           ============================================================
+# CHECK-YAML2PDB:             Showing 2 records
+# CHECK-YAML2PDB:             0x1000 | UNKNOWN RECORD (0xF123) [size = 12]
+# CHECK-YAML2PDB:                      bytes (
+# CHECK-YAML2PDB:                        0000: 0A0023F1 01234567 89ABCDEF                                               |..#..#Eg....|
+# CHECK-YAML2PDB:                      )
+# CHECK-YAML2PDB:             0x1001 | LF_ARGLIST [size = 12]
+# CHECK-YAML2PDB:                      0x0103 (std::nullptr_t): `std::nullptr_t`
+# CHECK-YAML2PDB-TYPE-DATA:            bytes (
+# CHECK-YAML2PDB-TYPE-DATA:              0000: 0A000112 01000000 03010000                                               |............|
+# CHECK-YAML2PDB-TYPE-DATA:            )
+
+# CHECK-PDB2YAML: TpiStream:
+# CHECK-PDB2YAML:   Version:         VC80
+# CHECK-PDB2YAML:   Records:
+# CHECK-PDB2YAML:     - Kind:            0xF123
+# CHECK-PDB2YAML:       UnknownLeaf:
+# CHECK-PDB2YAML:         Data:            0123456789ABCDEF
+# CHECK-PDB2YAML:     - Kind:            LF_ARGLIST
+# CHECK-PDB2YAML:       ArgList:
+# CHECK-PDB2YAML:         ArgIndices:      [ 259 ]
+
+---
+TpiStream:
+  Version:         VC80
+  Records:
+    - Kind:            0xF123
+      UnknownLeaf:
+        Data:            0123456789ABCDEF
+    - Kind:            LF_ARGLIST
+      ArgList:
+        ArgIndices:      [ 259 ]
+...
diff --git a/llvm/tools/llvm-pdbutil/MinimalSymbolDumper.cpp b/llvm/tools/llvm-pdbutil/MinimalSymbolDumper.cpp
index caed429f8bc4..9121ae54d467 100644
--- a/llvm/tools/llvm-pdbutil/MinimalSymbolDumper.cpp
+++ b/llvm/tools/llvm-pdbutil/MinimalSymbolDumper.cpp
@@ -396,14 +396,23 @@ Error MinimalSymbolDumper::visitSymbolBegin(codeview::CVSymbol &Record,
 }
 
 Error MinimalSymbolDumper::visitSymbolEnd(CVSymbol &Record) {
-  if (RecordBytes) {
-    AutoIndent Indent(P, 7);
-    P.formatBinary("bytes", Record.content(), 0);
-  }
+  if (RecordBytes)
+    printSymbolBytes(Record);
   P.Unindent();
   return Error::success();
 }
 
+Error MinimalSymbolDumper::visitUnknownSymbol(CVSymbol &Record) {
+  if (!RecordBytes)
+    printSymbolBytes(Record);
+  return Error::success();
+}
+
+void MinimalSymbolDumper::printSymbolBytes(CVSymbol &Record) const {
+  AutoIndent Indent(P, 7);
+  P.formatBinary("bytes", Record.content(), 0);
+}
+
 std::string MinimalSymbolDumper::typeOrIdIndex(codeview::TypeIndex TI,
                                                bool IsType) const {
   if (TI.isSimple() || TI.isDecoratedItemId())
diff --git a/llvm/tools/llvm-pdbutil/MinimalSymbolDumper.h b/llvm/tools/llvm-pdbutil/MinimalSymbolDumper.h
index cdc75c1cfba0..d653b547a589 100644
--- a/llvm/tools/llvm-pdbutil/MinimalSymbolDumper.h
+++ b/llvm/tools/llvm-pdbutil/MinimalSymbolDumper.h
@@ -36,6 +36,7 @@ public:
   Error visitSymbolBegin(codeview::CVSymbol &Record) override;
   Error visitSymbolBegin(codeview::CVSymbol &Record, uint32_t Offset) override;
   Error visitSymbolEnd(codeview::CVSymbol &Record) override;
+  Error visitUnknownSymbol(codeview::CVSymbol &Record) override;
 
   void setSymbolGroup(const SymbolGroup *Group) { SymGroup = Group; }
 
@@ -51,6 +52,8 @@ private:
   std::string typeIndex(codeview::TypeIndex TI) const;
   std::string idIndex(codeview::TypeIndex TI) const;
 
+  void printSymbolBytes(codeview::CVSymbol &Record) const;
+
   LinePrinter &P;
 
   /// Dumping certain records requires knowing what machine this is. The
diff --git a/llvm/tools/llvm-pdbutil/MinimalTypeDumper.cpp b/llvm/tools/llvm-pdbutil/MinimalTypeDumper.cpp
index 5f0f95b3775e..fc29ec46180c 100644
--- a/llvm/tools/llvm-pdbutil/MinimalTypeDumper.cpp
+++ b/llvm/tools/llvm-pdbutil/MinimalTypeDumper.cpp
@@ -261,11 +261,15 @@ Error MinimalTypeDumpVisitor::visitTypeBegin(CVType &Record, TypeIndex Index) {
 }
 
 Error MinimalTypeDumpVisitor::visitTypeEnd(CVType &Record) {
+  if (RecordBytes)
+    P.formatBinary("bytes", Record.RecordData, 0);
   P.Unindent(Width + 3);
-  if (RecordBytes) {
-    AutoIndent Indent(P, 9);
-    P.formatBinary("Bytes", Record.RecordData, 0);
-  }
+  return Error::success();
+}
+
+Error MinimalTypeDumpVisitor::visitUnknownType(CVType &Record) {
+  if (!RecordBytes)
+    P.formatBinary("bytes", Record.RecordData, 0);
   return Error::success();
 }
 
@@ -277,7 +281,15 @@ Error MinimalTypeDumpVisitor::visitMemberBegin(CVMemberRecord &Record) {
 Error MinimalTypeDumpVisitor::visitMemberEnd(CVMemberRecord &Record) {
   if (RecordBytes) {
     AutoIndent Indent(P, 2);
-    P.formatBinary("Bytes", Record.Data, 0);
+    P.formatBinary("bytes", Record.Data, 0);
+  }
+  return Error::success();
+}
+
+Error MinimalTypeDumpVisitor::visitUnknownMember(CVMemberRecord &Record) {
+  if (!RecordBytes) {
+    AutoIndent Indent(P, 2);
+    P.formatBinary("bytes", Record.Data, 0);
   }
   return Error::success();
 }
diff --git a/llvm/tools/llvm-pdbutil/MinimalTypeDumper.h b/llvm/tools/llvm-pdbutil/MinimalTypeDumper.h
index 6bc456d47ac4..7b06b7a0a71e 100644
--- a/llvm/tools/llvm-pdbutil/MinimalTypeDumper.h
+++ b/llvm/tools/llvm-pdbutil/MinimalTypeDumper.h
@@ -37,8 +37,11 @@ public:
   Error visitTypeBegin(codeview::CVType &Record,
                        codeview::TypeIndex Index) override;
   Error visitTypeEnd(codeview::CVType &Record) override;
+  Error visitUnknownType(codeview::CVType &Record) override;
+
   Error visitMemberBegin(codeview::CVMemberRecord &Record) override;
   Error visitMemberEnd(codeview::CVMemberRecord &Record) override;
+  Error visitUnknownMember(codeview::CVMemberRecord &Record) override;
 
 #define TYPE_RECORD(EnumName, EnumVal, Name)                                   \
   Error visitKnownRecord(codeview::CVType &CVR,                                \