--- a/src/cache.rs	Mon Feb 17 18:38:05 2020 +0100
+++ b/src/cache.rs	Mon Feb 17 19:36:18 2020 +0100
@@ -152,6 +152,7 @@
     }
 }
 
+
 pub type CacheKey = [u8; 16];
 pub type CacheID = u64;
 type CacheEntry<T> = (T, LRUHandle<CacheKey>);
@@ -237,6 +238,16 @@
     }
 }
 
+
+// The compiler does not automatically derive Send and Sync for Cache because it contains
+// raw pointers.
+// These raw pointers are only pointing to the elements hold in the same cache and insertion
+// clones the values. It is therefore safe to implement Send for Cache.
+// Since all functions that access these raw pointers are mutable member functions, it is also safe to implement Sync
+// (Sync is defined as "if &T is Send-able")
+unsafe impl<T: Send> Send for Cache<T> {}
+unsafe impl<T: Sync> Sync for Cache<T> {}
+
 #[cfg(test)]
 mod tests {
     use super::LRUList;

--- a/src/types.rs	Mon Feb 17 18:38:05 2020 +0100
+++ b/src/types.rs	Mon Feb 17 19:36:18 2020 +0100
@@ -10,7 +10,7 @@
 use std::sync::Arc;
 use std::sync::RwLock;
 
-pub trait RandomAccess : Send {
+pub trait RandomAccess : Send + Sync {
     fn read_at(&self, off: usize, dst: &mut [u8]) -> Result<usize>;
 }
 
@@ -48,7 +48,7 @@
     }
 }
 
-/// A shared thingy with interior mutability.
+/// A shared thingy with guarded by a lock.
 pub type Shared<T> = Arc<RwLock<T>>;
 
 pub fn share<T>(t: T) -> Arc<RwLock<T>> {