diff --git a/Cargo.lock b/Cargo.lock
index 4bd99b7fbe7..1aa0b2ea4a3 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1775,9 +1775,9 @@ checksum = "ce23b50ad8242c51a442f3ff322d56b02f08852c77e4c0b4d3fd684abc89c683"
 
 [[package]]
 name = "indexmap"
-version = "2.2.6"
+version = "2.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "168fb715dda47215e360912c096649d23d58bf392ac62f73919e831745e40f26"
+checksum = "93ead53efc7ea8ed3cfb0c79fc8023fbb782a5432b52830b6518941cebe6505c"
 dependencies = [
  "equivalent",
  "hashbrown",
diff --git a/compiler/rustc_data_structures/Cargo.toml b/compiler/rustc_data_structures/Cargo.toml
index 3794a6e043c..69cbf8c4161 100644
--- a/compiler/rustc_data_structures/Cargo.toml
+++ b/compiler/rustc_data_structures/Cargo.toml
@@ -10,7 +10,7 @@ bitflags = "2.4.1"
 either = "1.0"
 elsa = "=1.7.1"
 ena = "0.14.3"
-indexmap = { version = "2.0.0" }
+indexmap = { version = "2.4.0" }
 jobserver_crate = { version = "0.1.28", package = "jobserver" }
 measureme = "11"
 rustc-hash = "1.1.0"
diff --git a/compiler/rustc_monomorphize/src/partitioning.rs b/compiler/rustc_monomorphize/src/partitioning.rs
index 65a3d8d1742..92902185e8b 100644
--- a/compiler/rustc_monomorphize/src/partitioning.rs
+++ b/compiler/rustc_monomorphize/src/partitioning.rs
@@ -371,7 +371,7 @@ fn merge_codegen_units<'tcx>(
         // Move the items from `cgu_src` to `cgu_dst`. Some of them may be
         // duplicate inlined items, in which case the destination CGU is
         // unaffected. Recalculate size estimates afterwards.
-        cgu_dst.items_mut().extend(cgu_src.items_mut().drain(..));
+        cgu_dst.items_mut().append(cgu_src.items_mut());
         cgu_dst.compute_size_estimate();
 
         // Record that `cgu_dst` now contains all the stuff that was in
@@ -410,7 +410,7 @@ fn merge_codegen_units<'tcx>(
         // Move the items from `smallest` to `second_smallest`. Some of them
         // may be duplicate inlined items, in which case the destination CGU is
         // unaffected. Recalculate size estimates afterwards.
-        second_smallest.items_mut().extend(smallest.items_mut().drain(..));
+        second_smallest.items_mut().append(smallest.items_mut());
         second_smallest.compute_size_estimate();
 
         // Don't update `cgu_contents`, that's only for incremental builds.