diff --git a/clang/tools/driver/cc1as_main.cpp b/clang/tools/driver/cc1as_main.cpp
index bc398fa0731f1..a55e06500d9d9 100644
--- a/clang/tools/driver/cc1as_main.cpp
+++ b/clang/tools/driver/cc1as_main.cpp
@@ -89,10 +89,15 @@ struct AssemblerInvocation {
   /// @{
 
   std::vector<std::string> IncludePaths;
+  LLVM_PREFERRED_TYPE(bool)
   unsigned NoInitialTextSection : 1;
+  LLVM_PREFERRED_TYPE(bool)
   unsigned SaveTemporaryLabels : 1;
+  LLVM_PREFERRED_TYPE(bool)
   unsigned GenDwarfForAssembly : 1;
+  LLVM_PREFERRED_TYPE(bool)
   unsigned RelaxELFRelocations : 1;
+  LLVM_PREFERRED_TYPE(bool)
   unsigned Dwarf64 : 1;
   unsigned DwarfVersion;
   std::string DwarfDebugFlags;
@@ -117,7 +122,9 @@ struct AssemblerInvocation {
     FT_Obj   ///< Object file output.
   };
   FileType OutputType;
+  LLVM_PREFERRED_TYPE(bool)
   unsigned ShowHelp : 1;
+  LLVM_PREFERRED_TYPE(bool)
   unsigned ShowVersion : 1;
 
   /// @}
@@ -125,19 +132,28 @@ struct AssemblerInvocation {
   /// @{
 
   unsigned OutputAsmVariant;
+  LLVM_PREFERRED_TYPE(bool)
   unsigned ShowEncoding : 1;
+  LLVM_PREFERRED_TYPE(bool)
   unsigned ShowInst : 1;
 
   /// @}
   /// @name Assembler Options
   /// @{
 
+  LLVM_PREFERRED_TYPE(bool)
   unsigned RelaxAll : 1;
+  LLVM_PREFERRED_TYPE(bool)
   unsigned NoExecStack : 1;
+  LLVM_PREFERRED_TYPE(bool)
   unsigned FatalWarnings : 1;
+  LLVM_PREFERRED_TYPE(bool)
   unsigned NoWarn : 1;
+  LLVM_PREFERRED_TYPE(bool)
   unsigned NoTypeCheck : 1;
+  LLVM_PREFERRED_TYPE(bool)
   unsigned IncrementalLinkerCompatible : 1;
+  LLVM_PREFERRED_TYPE(bool)
   unsigned EmbedBitcode : 1;
 
   /// Whether to emit DWARF unwind info.
@@ -145,6 +161,7 @@ struct AssemblerInvocation {
 
   // Whether to emit compact-unwind for non-canonical entries.
   // Note: maybe overriden by other constraints.
+  LLVM_PREFERRED_TYPE(bool)
   unsigned EmitCompactUnwindNonCanonical : 1;
 
   /// The name of the relocation model to use.