diff --git a/src/msf/mod.rs b/src/msf/mod.rs
index e00ca44..92b6db3 100644
--- a/src/msf/mod.rs
+++ b/src/msf/mod.rs
@@ -55,11 +55,14 @@ enum StreamTable<'s> {
 
     // Given the table location, we can access the stream table itself
     Available {
-        stream_table_view: Box<dyn SourceView<'s>>,
+        stream_table_view: Box<dyn SourceView<'s> + Send>,
     },
 }
 
-fn view<'s>(source: &mut dyn Source<'s>, page_list: &PageList) -> Result<Box<dyn SourceView<'s>>> {
+fn view<'s>(
+    source: &mut dyn Source<'s>,
+    page_list: &PageList,
+) -> Result<Box<dyn SourceView<'s> + Send + Sync>> {
     // view it
     let view = source.view(page_list.source_slices())?;
 
@@ -120,7 +123,10 @@ mod big {
     }
 
     impl<'s, S: Source<'s>> BigMSF<'s, S> {
-        pub fn new(source: S, header_view: Box<dyn SourceView<'_>>) -> Result<BigMSF<'s, S>> {
+        pub fn new(
+            source: S,
+            header_view: Box<dyn SourceView<'_> + Send>,
+        ) -> Result<BigMSF<'s, S>> {
             let mut buf = ParseBuffer::from(header_view.as_slice());
             let header: RawHeader = buf.parse()?;
 
@@ -345,7 +351,7 @@ mod small {
 /// Represents a single Stream within the multi-stream file.
 #[derive(Debug)]
 pub struct Stream<'s> {
-    source_view: Box<dyn SourceView<'s>>,
+    source_view: Box<dyn SourceView<'s> + Send + Sync>,
 }
 
 impl<'s> Stream<'s> {
@@ -380,7 +386,9 @@ fn header_matches(actual: &[u8], expected: &[u8]) -> bool {
     actual.len() >= expected.len() && &actual[0..expected.len()] == expected
 }
 
-pub fn open_msf<'s, S: Source<'s> + 's>(mut source: S) -> Result<Box<dyn Msf<'s, S> + 's>> {
+pub fn open_msf<'s, S: Source<'s> + Send + 's>(
+    mut source: S,
+) -> Result<Box<dyn Msf<'s, S> + Send + 's>> {
     // map the header
     let mut header_location = PageList::new(4096);
     header_location.push(0);
diff --git a/src/pdb.rs b/src/pdb.rs
index b92f671..762ff82 100644
--- a/src/pdb.rs
+++ b/src/pdb.rs
@@ -34,7 +34,7 @@ const IPI_STREAM: u32 = 4;
 #[derive(Debug)]
 pub struct PDB<'s, S> {
     /// `msf` provides access to the underlying data streams
-    msf: Box<dyn Msf<'s, S> + 's>,
+    msf: Box<dyn Msf<'s, S> + Send + 's>,
 
     /// Memoize the `dbi::Header`, since it contains stream numbers we sometimes need
     dbi_header: Option<DBIHeader>,
@@ -43,6 +43,14 @@ pub struct PDB<'s, S> {
     dbi_extra_streams: Option<DBIExtraStreams>,
 }
 
+// Assert that the PDB type is Send.
+const _: fn() = || {
+    fn assert<T: ?Sized + Send>() {}
+    // Use a dummy *const () for `S` as that will be !Send and !Sync.
+    // In practice (e.g. to make a PDB) `S` will need to be Send, but it doesn't matter here.
+    assert::<PDB<*const ()>>();
+};
+
 impl<'s, S: Source<'s> + 's> PDB<'s, S> {
     /// Create a new `PDB` for a `Source`.
     ///
@@ -56,7 +64,10 @@ impl<'s, S: Source<'s> + 's> PDB<'s, S> {
     /// * `Error::UnrecognizedFileFormat` if the `Source` does not appear to be a PDB file
     /// * `Error::IoError` if returned by the `Source`
     /// * `Error::PageReferenceOutOfRange`, `Error::InvalidPageSize` if the PDB file seems corrupt
-    pub fn open(source: S) -> Result<PDB<'s, S>> {
+    pub fn open(source: S) -> Result<PDB<'s, S>>
+    where
+        S: Send,
+    {
         Ok(PDB {
             msf: msf::open_msf(source)?,
             dbi_header: None,
diff --git a/src/source.rs b/src/source.rs
index 69dae13..47453ac 100644
--- a/src/source.rs
+++ b/src/source.rs
@@ -51,7 +51,10 @@ pub trait Source<'s>: fmt::Debug {
     ///
     /// Note that the SourceView's as_slice() method cannot fail, so `view()` is the time to raise
     /// IO errors.
-    fn view(&mut self, slices: &[SourceSlice]) -> Result<Box<dyn SourceView<'s>>, io::Error>;
+    fn view(
+        &mut self,
+        slices: &[SourceSlice],
+    ) -> Result<Box<dyn SourceView<'s> + Send + Sync>, io::Error>;
 }
 
 /// An owned, droppable, read-only view of the source file which can be referenced as a byte slice.
@@ -81,7 +84,10 @@ impl<'s, T> Source<'s> for T
 where
     T: io::Read + io::Seek + fmt::Debug + 's,
 {
-    fn view(&mut self, slices: &[SourceSlice]) -> Result<Box<dyn SourceView<'s>>, io::Error> {
+    fn view(
+        &mut self,
+        slices: &[SourceSlice],
+    ) -> Result<Box<dyn SourceView<'s> + Send + Sync>, io::Error> {
         let len = slices.iter().fold(0, |acc, s| acc + s.size);
 
         let mut v = ReadView {