diff --git a/mmtk/Cargo.toml b/mmtk/Cargo.toml
index 1c49523..c1d2d80 100644
--- a/mmtk/Cargo.toml
+++ b/mmtk/Cargo.toml
@@ -37,7 +37,7 @@ features = ["is_mmtk_object", "object_pinning"]
 
 # Uncomment the following lines to use mmtk-core from the official repository.
 git = "https://github.com/udesou/mmtk-core"
-rev = "b82a596"
+rev = "e9660c7"
 
 # Uncomment the following line to use mmtk-core from a local repository.
 #path = "../../mmtk-core"
diff --git a/mmtk/src/collection.rs b/mmtk/src/collection.rs
index 96fa042..3995975 100644
--- a/mmtk/src/collection.rs
+++ b/mmtk/src/collection.rs
@@ -12,8 +12,8 @@ use std::thread;
 pub struct VMCollection {}
 
 impl Collection<Ruby> for VMCollection {
-    fn is_collection_disabled() -> bool {
-        !crate::BINDING_FAST.gc_enabled.load(Ordering::Relaxed)
+    fn is_collection_enabled() -> bool {
+        crate::BINDING_FAST.gc_enabled.load(Ordering::Relaxed)
     }
 
     fn stop_all_mutators<F>(tls: VMWorkerThread, mut mutator_visitor: F)