diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -15902,9 +15902,10 @@
 
       // If the types are still not compatible, we need to test whether the
       // promoted type and the underlying type are the same except for
-      // signedness. Ask the AST for the correctly corresponding type and see
-      // if that's compatible.
+      // signedness except for boolean. Ask the AST for the correctly corresponding
+      // type and see if that's compatible.
       if (!PromoteType.isNull() &&
+          !UnderlyingType->isBooleanType() &&
           PromoteType->isUnsignedIntegerType() !=
               UnderlyingType->isUnsignedIntegerType()) {
         UnderlyingType =
diff --git a/clang/test/SemaCXX/varargs.cpp b/clang/test/SemaCXX/varargs.cpp
--- a/clang/test/SemaCXX/varargs.cpp
+++ b/clang/test/SemaCXX/varargs.cpp
@@ -53,6 +53,8 @@
 
   // Ensure that signed vs unsigned doesn't matter either.
   (void)__builtin_va_arg(ap, unsigned int);
+
+  (void)__builtin_va_arg(ap, bool); // expected-warning {{second argument to 'va_arg' is of promotable type 'bool'; this va_arg has undefined behavior because arguments will be promoted to 'int'}}
 }
 
 #if __cplusplus >= 201103L