diff --git a/src/cargo/core/package_id.rs b/src/cargo/core/package_id.rs
index 7231c137251..885d2c61caf 100644
--- a/src/cargo/core/package_id.rs
+++ b/src/cargo/core/package_id.rs
@@ -3,6 +3,7 @@ use std::fmt::{self, Formatter};
 use std::hash;
 use std::hash::Hash;
 use std::path::Path;
+use std::ptr;
 use std::sync::Mutex;
 
 use semver;
@@ -18,7 +19,7 @@ lazy_static! {
 }
 
 /// Identifier for a specific version of a package in a specific source.
-#[derive(Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
+#[derive(Clone, Copy, Eq, Hash, PartialOrd, Ord)]
 pub struct PackageId {
     inner: &'static PackageIdInner,
 }
@@ -96,6 +97,15 @@ impl<'de> de::Deserialize<'de> for PackageId {
     }
 }
 
+impl PartialEq for PackageId {
+    fn eq(&self, other: &PackageId) -> bool {
+        if ptr::eq(self.inner, other.inner) {
+            return true;
+        }
+        (*self.inner).eq(&*other.inner)
+    }
+}
+
 impl PackageId {
     pub fn new<T: ToSemver>(name: &str, version: T, sid: SourceId) -> CargoResult<PackageId> {
         let v = version.to_semver()?;