diff --git a/clang/lib/ASTMatchers/Dynamic/Marshallers.h b/clang/lib/ASTMatchers/Dynamic/Marshallers.h
--- a/clang/lib/ASTMatchers/Dynamic/Marshallers.h
+++ b/clang/lib/ASTMatchers/Dynamic/Marshallers.h
@@ -524,8 +524,9 @@
       }
       return {};
     }
-    InnerArgs.set_size(i + 1);
-    InnerArgsPtr[i] = new (&InnerArgs[i]) ArgT(ArgTraits::get(Value));
+    assert(InnerArgs.size() < InnerArgs.capacity());
+    InnerArgs.emplace_back(ArgTraits::get(Value));
+    InnerArgsPtr[i] = &InnerArgs[i];
   }
   return outvalueToVariantMatcher(Func(InnerArgsPtr));
 }