diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h
@@ -346,7 +346,7 @@
 
   lldb::CompUnitSP ParseCompileUnit(DWARFCompileUnit &dwarf_cu);
 
-  virtual DWARFUnit *
+  virtual DWARFCompileUnit *
   GetDWARFCompileUnit(lldb_private::CompileUnit *comp_unit);
 
   DWARFUnit *GetNextUnparsedDWARFCompileUnit(DWARFUnit *prev_cu);
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
@@ -632,8 +632,7 @@
   return *m_info;
 }
 
-DWARFUnit *
-SymbolFileDWARF::GetDWARFCompileUnit(lldb_private::CompileUnit *comp_unit) {
+DWARFCompileUnit *SymbolFileDWARF::GetDWARFCompileUnit(CompileUnit *comp_unit) {
   if (!comp_unit)
     return nullptr;
 
@@ -641,7 +640,9 @@
   DWARFUnit *dwarf_cu = DebugInfo().GetUnitAtIndex(comp_unit->GetID());
   if (dwarf_cu && dwarf_cu->GetUserData() == nullptr)
     dwarf_cu->SetUserData(comp_unit);
-  return dwarf_cu;
+
+  // It must be DWARFCompileUnit when it created a CompileUnit.
+  return llvm::cast_or_null<DWARFCompileUnit>(dwarf_cu);
 }
 
 DWARFDebugRanges *SymbolFileDWARF::GetDebugRanges() {
@@ -1599,8 +1600,7 @@
 llvm::Optional<uint64_t> SymbolFileDWARF::GetDWOId() {
   if (GetNumCompileUnits() == 1) {
     if (auto comp_unit = GetCompileUnitAtIndex(0))
-      if (DWARFCompileUnit *cu = llvm::dyn_cast_or_null<DWARFCompileUnit>(
-              GetDWARFCompileUnit(comp_unit.get())))
+      if (DWARFCompileUnit *cu = GetDWARFCompileUnit(comp_unit.get()))
         if (DWARFDebugInfoEntry *cu_die = cu->DIE().GetDIE())
           if (uint64_t dwo_id = ::GetDWOId(*cu, *cu_die))
             return dwo_id;