diff --git a/libimagref/src/error.rs b/libimagref/src/error.rs
index 50c0723a..4fee1429 100644
--- a/libimagref/src/error.rs
+++ b/libimagref/src/error.rs
@@ -2,6 +2,7 @@ generate_error_module!(
     generate_error_types!(RefError, RefErrorKind,
         StoreReadError          => "Store read error",
         StoreWriteError         => "Store write error",
+        IOError                 => "IO Error",
         HeaderTypeError         => "Header type error",
         HeaderFieldMissingError => "Header field missing error",
         HeaderFieldWriteError   => "Header field cannot be written",
diff --git a/libimagref/src/reference.rs b/libimagref/src/reference.rs
index 9d15dfd6..fb0d34eb 100644
--- a/libimagref/src/reference.rs
+++ b/libimagref/src/reference.rs
@@ -223,8 +223,31 @@ impl<'a> Ref<'a> {
     }
 
     /// Check whether the Hashsum of the referenced file is equal to the stored hashsum
-    pub fn fs_link_valid_hash(&self) -> bool {
-        unimplemented!()
+    pub fn fs_link_valid_hash(&self) -> Result<bool> {
+        let stored_hash = try!(match self.0.get_header().read("ref.content_hash") {
+            // content hash stored...
+            Ok(Some(Value::String(s))) => Ok(s),
+
+            // content hash header field has wrong type
+            Ok(Some(_)) => Err(REK::HeaderTypeError.into_error()),
+
+            // content hash not stored
+            Ok(None) => Err(REK::HeaderFieldMissingError.into_error()),
+
+            // Error
+            Err(e) => Err(REK::StoreReadError.into_error_with_cause(Box::new(e))),
+        });
+
+        let current_hash = try!(self.fs_file()
+            .and_then(|pb| {
+                File::open(pb)
+                    .map_err(Box::new)
+                    .map_err(|e| REK::IOError.into_error_with_cause(e))
+            })
+            .map(|mut file| hash_file_contents(&mut file))
+        );
+
+        Ok(stored_hash == current_hash)
     }
 
     /// Update the Ref by re-checking the file from FS