diff --git a/Cargo.toml b/Cargo.toml
index 3dd659db4..798901b5c 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "rustc-rayon"
-version = "0.5.0"
+version = "0.5.1"
 authors = ["Niko Matsakis <niko@alum.mit.edu>",
            "Josh Stone <cuviper@gmail.com>"]
 description = "Simple work-stealing parallelism for Rust - fork for rustc"
@@ -22,6 +22,7 @@ exclude = ["ci"]
 name = "rayon"
 
 [dependencies]
+indexmap = { version = "2", optional = true }
 rustc-rayon-core = { version = "0.5", path = "rayon-core" }
 
 # This is a public dependency!
diff --git a/src/lib.rs b/src/lib.rs
index 86f997b36..7ba0a9b3d 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -110,6 +110,7 @@ pub mod vec;
 
 mod math;
 mod par_either;
+mod par_indexmap;
 
 mod compile_fail;
 
diff --git a/src/par_indexmap.rs b/src/par_indexmap.rs
new file mode 100644
index 000000000..fb03ac18d
--- /dev/null
+++ b/src/par_indexmap.rs
@@ -0,0 +1,230 @@
+#![cfg(feature = "indexmap")]
+//! Minimal `indexmap` support for `rustc-rayon`
+
+use crate::iter::plumbing::{bridge, Consumer, Producer, ProducerCallback, UnindexedConsumer};
+use crate::iter::{IndexedParallelIterator, IntoParallelIterator, ParallelIterator};
+
+mod map {
+    use super::*;
+    use indexmap::map::{IndexMap, Iter, IterMut, Slice};
+
+    impl<'a, K, V, S> IntoParallelIterator for &'a IndexMap<K, V, S>
+    where
+        K: Sync,
+        V: Sync,
+    {
+        type Item = (&'a K, &'a V);
+        type Iter = ParIter<'a, K, V>;
+
+        fn into_par_iter(self) -> Self::Iter {
+            ParIter {
+                slice: self.as_slice(),
+            }
+        }
+    }
+
+    #[derive(Debug)]
+    pub struct ParIter<'a, K, V> {
+        slice: &'a Slice<K, V>,
+    }
+
+    impl<'a, K: Sync, V: Sync> ParallelIterator for ParIter<'a, K, V> {
+        type Item = (&'a K, &'a V);
+
+        fn drive_unindexed<C>(self, consumer: C) -> C::Result
+        where
+            C: UnindexedConsumer<Self::Item>,
+        {
+            bridge(self, consumer)
+        }
+
+        fn opt_len(&self) -> Option<usize> {
+            Some(self.slice.len())
+        }
+    }
+
+    impl<K: Sync, V: Sync> IndexedParallelIterator for ParIter<'_, K, V> {
+        fn drive<C>(self, consumer: C) -> C::Result
+        where
+            C: Consumer<Self::Item>,
+        {
+            bridge(self, consumer)
+        }
+
+        fn len(&self) -> usize {
+            self.slice.len()
+        }
+
+        fn with_producer<CB>(self, callback: CB) -> CB::Output
+        where
+            CB: ProducerCallback<Self::Item>,
+        {
+            callback.callback(IterProducer { slice: self.slice })
+        }
+    }
+
+    struct IterProducer<'a, K, V> {
+        slice: &'a Slice<K, V>,
+    }
+
+    impl<'a, K: Sync, V: Sync> Producer for IterProducer<'a, K, V> {
+        type Item = (&'a K, &'a V);
+        type IntoIter = Iter<'a, K, V>;
+
+        fn into_iter(self) -> Self::IntoIter {
+            self.slice.iter()
+        }
+
+        fn split_at(self, index: usize) -> (Self, Self) {
+            let (left, right) = self.slice.split_at(index);
+            (Self { slice: left }, Self { slice: right })
+        }
+    }
+
+    impl<'a, K, V, S> IntoParallelIterator for &'a mut IndexMap<K, V, S>
+    where
+        K: Sync + Send,
+        V: Send,
+    {
+        type Item = (&'a K, &'a mut V);
+        type Iter = ParIterMut<'a, K, V>;
+
+        fn into_par_iter(self) -> Self::Iter {
+            ParIterMut {
+                slice: self.as_mut_slice(),
+            }
+        }
+    }
+
+    #[derive(Debug)]
+    pub struct ParIterMut<'a, K, V> {
+        slice: &'a mut Slice<K, V>,
+    }
+
+    impl<'a, K: Sync + Send, V: Send> ParallelIterator for ParIterMut<'a, K, V> {
+        type Item = (&'a K, &'a mut V);
+
+        fn drive_unindexed<C>(self, consumer: C) -> C::Result
+        where
+            C: UnindexedConsumer<Self::Item>,
+        {
+            bridge(self, consumer)
+        }
+
+        fn opt_len(&self) -> Option<usize> {
+            Some(self.slice.len())
+        }
+    }
+
+    impl<K: Sync + Send, V: Send> IndexedParallelIterator for ParIterMut<'_, K, V> {
+        fn drive<C>(self, consumer: C) -> C::Result
+        where
+            C: Consumer<Self::Item>,
+        {
+            bridge(self, consumer)
+        }
+
+        fn len(&self) -> usize {
+            self.slice.len()
+        }
+
+        fn with_producer<CB>(self, callback: CB) -> CB::Output
+        where
+            CB: ProducerCallback<Self::Item>,
+        {
+            callback.callback(IterMutProducer { slice: self.slice })
+        }
+    }
+
+    struct IterMutProducer<'a, K, V> {
+        slice: &'a mut Slice<K, V>,
+    }
+
+    impl<'a, K: Sync + Send, V: Send> Producer for IterMutProducer<'a, K, V> {
+        type Item = (&'a K, &'a mut V);
+        type IntoIter = IterMut<'a, K, V>;
+
+        fn into_iter(self) -> Self::IntoIter {
+            self.slice.iter_mut()
+        }
+
+        fn split_at(self, index: usize) -> (Self, Self) {
+            let (left, right) = self.slice.split_at_mut(index);
+            (Self { slice: left }, Self { slice: right })
+        }
+    }
+}
+
+mod set {
+    use super::*;
+    use indexmap::set::{IndexSet, Iter, Slice};
+
+    impl<'a, T: Sync, S> IntoParallelIterator for &'a IndexSet<T, S> {
+        type Item = &'a T;
+        type Iter = ParIter<'a, T>;
+
+        fn into_par_iter(self) -> Self::Iter {
+            ParIter {
+                slice: self.as_slice(),
+            }
+        }
+    }
+
+    #[derive(Debug)]
+    pub struct ParIter<'a, T> {
+        slice: &'a Slice<T>,
+    }
+
+    impl<'a, T: Sync> ParallelIterator for ParIter<'a, T> {
+        type Item = &'a T;
+
+        fn drive_unindexed<C>(self, consumer: C) -> C::Result
+        where
+            C: UnindexedConsumer<Self::Item>,
+        {
+            bridge(self, consumer)
+        }
+
+        fn opt_len(&self) -> Option<usize> {
+            Some(self.slice.len())
+        }
+    }
+
+    impl<T: Sync> IndexedParallelIterator for ParIter<'_, T> {
+        fn drive<C>(self, consumer: C) -> C::Result
+        where
+            C: Consumer<Self::Item>,
+        {
+            bridge(self, consumer)
+        }
+
+        fn len(&self) -> usize {
+            self.slice.len()
+        }
+
+        fn with_producer<CB>(self, callback: CB) -> CB::Output
+        where
+            CB: ProducerCallback<Self::Item>,
+        {
+            callback.callback(IterProducer { slice: self.slice })
+        }
+    }
+
+    struct IterProducer<'a, T> {
+        slice: &'a Slice<T>,
+    }
+
+    impl<'a, T: Sync> Producer for IterProducer<'a, T> {
+        type Item = &'a T;
+        type IntoIter = Iter<'a, T>;
+
+        fn into_iter(self) -> Self::IntoIter {
+            self.slice.iter()
+        }
+
+        fn split_at(self, index: usize) -> (Self, Self) {
+            let (left, right) = self.slice.split_at(index);
+            (Self { slice: left }, Self { slice: right })
+        }
+    }
+}