diff --git a/libcxx/include/__algorithm/sort.h b/libcxx/include/__algorithm/sort.h
--- a/libcxx/include/__algorithm/sort.h
+++ b/libcxx/include/__algorithm/sort.h
@@ -737,7 +737,10 @@
     }
     // Use insertion sort if the length of the range is below the specified limit.
     if (__len < __limit) {
-      if (__leftmost) {
+      // TODO: Invalid comparison predicates can cause __insertion_sort_unguarded to go out-of-bounds, which is
+      //       highly undesirable. Disable this optimization until we at least have a way to assert that we're
+      //       not going out of bounds.
+      if (__leftmost || true) {
         std::__insertion_sort<_AlgPolicy, _Compare>(__first, __last, __comp);
       } else {
         std::__insertion_sort_unguarded<_AlgPolicy, _Compare>(__first, __last, __comp);