diff --git a/crates/keyfork-shard/src/openpgp.rs b/crates/keyfork-shard/src/openpgp.rs
index 70724c9..ccfefe9 100644
--- a/crates/keyfork-shard/src/openpgp.rs
+++ b/crates/keyfork-shard/src/openpgp.rs
@@ -194,33 +194,35 @@ impl<P: PromptHandler> OpenPGP<P> {
 }
 
 impl<P: PromptHandler> OpenPGP<P> {
-    /// Read all OpenPGP certificates in a path and return a [`Vec`] of them. Certificates are read
-    /// from a file, or from files one level deep in a directory.
+    /// Read all OpenPGP certificates in a path and return a [`Vec`] of them.
+    ///
+    /// Certificates are read from a file, or from files one level deep in a directory.
+    /// Certificates with duplicated fingerprints will be discarded.
     ///
     /// # Errors
-    /// The function may return an error if it is unable to read the directory or if Sequoia is unable
-    /// to load certificates from the file.
+    /// The function may return an error if it is unable to read the directory or if Sequoia is
+    /// unable to load certificates from the file.
     pub fn discover_certs(path: impl AsRef<Path>) -> Result<Vec<Cert>> {
         let path = path.as_ref();
 
+        let mut certs = HashMap::new();
         if path.is_file() {
-            let mut vec = vec![];
-            for cert in CertParser::from_file(path).map_err(Error::Sequoia)? {
-                vec.push(cert.map_err(Error::Sequoia)?);
+            for maybe_cert in CertParser::from_file(path).map_err(Error::Sequoia)? {
+                let cert = maybe_cert.map_err(Error::Sequoia)?;
+                certs.insert(cert.fingerprint(), cert);
             }
-            Ok(vec)
         } else {
-            let mut vec = vec![];
             for entry in path
                 .read_dir()
                 .map_err(Error::Io)?
                 .filter_map(Result::ok)
                 .filter(|p| p.path().is_file())
             {
-                vec.push(Cert::from_file(entry.path()).map_err(Error::Sequoia)?);
+                let cert = Cert::from_file(entry.path()).map_err(Error::Sequoia)?;
+                certs.insert(cert.fingerprint(), cert);
             }
-            Ok(vec)
         }
+        Ok(certs.into_values().collect())
     }
 }