diff --git a/clang/lib/Sema/SemaConcept.cpp b/clang/lib/Sema/SemaConcept.cpp
index 15b9c97489e7f..543bd450c554e 100644
--- a/clang/lib/Sema/SemaConcept.cpp
+++ b/clang/lib/Sema/SemaConcept.cpp
@@ -1999,8 +1999,9 @@ FormulaType SubsumptionChecker::Normalize(const NormalizedConstraint &NC) {
   });
 
   if (NC.getCompoundKind() == FormulaType::Kind) {
+    auto SizeLeft = Left.size();
     Res = std::move(Left);
-    Res.reserve(Left.size() + Right.size());
+    Res.reserve(SizeLeft + Right.size());
     std::for_each(std::make_move_iterator(Right.begin()),
                   std::make_move_iterator(Right.end()), Add);
     return Res;