diff --git a/mmtk/Cargo.lock b/mmtk/Cargo.lock
index 61e47a6..6d1610a 100644
--- a/mmtk/Cargo.lock
+++ b/mmtk/Cargo.lock
@@ -432,7 +432,7 @@ dependencies = [
 [[package]]
 name = "mmtk"
 version = "0.26.0"
-source = "git+https://github.com/mmtk/mmtk-core.git?rev=a3a72f8e5795678eff06fdc1524f0b429a62ccc0#a3a72f8e5795678eff06fdc1524f0b429a62ccc0"
+source = "git+https://github.com/mmtk/mmtk-core.git?rev=5edfd858c2539db5698fbc2e8cc1c5b74d951e99#5edfd858c2539db5698fbc2e8cc1c5b74d951e99"
 dependencies = [
  "atomic",
  "atomic-traits",
@@ -467,7 +467,7 @@ dependencies = [
 [[package]]
 name = "mmtk-macros"
 version = "0.26.0"
-source = "git+https://github.com/mmtk/mmtk-core.git?rev=a3a72f8e5795678eff06fdc1524f0b429a62ccc0#a3a72f8e5795678eff06fdc1524f0b429a62ccc0"
+source = "git+https://github.com/mmtk/mmtk-core.git?rev=5edfd858c2539db5698fbc2e8cc1c5b74d951e99#5edfd858c2539db5698fbc2e8cc1c5b74d951e99"
 dependencies = [
  "proc-macro-error",
  "proc-macro2",
diff --git a/mmtk/Cargo.toml b/mmtk/Cargo.toml
index d676597..bf65b4f 100644
--- a/mmtk/Cargo.toml
+++ b/mmtk/Cargo.toml
@@ -37,7 +37,7 @@ features = ["is_mmtk_object", "object_pinning", "sticky_immix_non_moving_nursery
 
 # Uncomment the following lines to use mmtk-core from the official repository.
 git = "https://github.com/mmtk/mmtk-core.git"
-rev = "a3a72f8e5795678eff06fdc1524f0b429a62ccc0"
+rev = "5edfd858c2539db5698fbc2e8cc1c5b74d951e99"
 
 # Uncomment the following line to use mmtk-core from a local repository.
 # path = "../../mmtk-core"
diff --git a/mmtk/src/api.rs b/mmtk/src/api.rs
index 98ea969..2b2500a 100644
--- a/mmtk/src/api.rs
+++ b/mmtk/src/api.rs
@@ -241,7 +241,7 @@ pub extern "C" fn mmtk_get_forwarded_object(object: ObjectReference) -> Nullable
 pub extern "C" fn mmtk_is_mmtk_object(addr: Address) -> bool {
     debug_assert!(!addr.is_zero());
     debug_assert!(addr.is_aligned_to(mmtk::util::is_mmtk_object::VO_BIT_REGION_SIZE));
-    memory_manager::is_mmtk_object(addr)
+    memory_manager::is_mmtk_object(addr).is_some()
 }
 
 #[no_mangle]
diff --git a/mmtk/src/scanning.rs b/mmtk/src/scanning.rs
index 991bb7a..3fb8ca1 100644
--- a/mmtk/src/scanning.rs
+++ b/mmtk/src/scanning.rs
@@ -28,7 +28,7 @@ impl Scanning<Ruby> for VMScanning {
         object_tracer: &mut OT,
     ) {
         debug_assert!(
-            mmtk::memory_manager::is_mmtk_object(object.to_raw_address()),
+            mmtk::memory_manager::is_mmtk_object(object.to_raw_address()).is_some(),
             "Not an MMTk object: {object}",
         );
         let gc_tls = unsafe { GCThreadTLS::from_vwt_check(tls) };
@@ -40,7 +40,7 @@ impl Scanning<Ruby> for VMScanning {
                 if pin { " pin" } else { "" }
             );
             debug_assert!(
-                mmtk::memory_manager::is_mmtk_object(target_object.to_raw_address()),
+                mmtk::memory_manager::is_mmtk_object(target_object.to_raw_address()).is_some(),
                 "Destination is not an MMTk object. Src: {object} dst: {target_object}"
             );
             let forwarded_target = object_tracer.trace_object(target_object);
@@ -173,7 +173,7 @@ impl VMScanning {
                 }
             );
             debug_assert!(
-                mmtk::memory_manager::is_mmtk_object(object.to_raw_address()),
+                mmtk::memory_manager::is_mmtk_object(object.to_raw_address()).is_some(),
                 "Root does not point to MMTk object.  object: {object}"
             );
             buffer.push(object);
diff --git a/mmtk/src/weak_proc.rs b/mmtk/src/weak_proc.rs
index fb04f1d..f231a7d 100644
--- a/mmtk/src/weak_proc.rs
+++ b/mmtk/src/weak_proc.rs
@@ -230,7 +230,7 @@ trait GlobalTableProcessingWork {
         // of `trace_object` due to the way it is used in `UPDATE_IF_MOVED`.
         let forward_object = |_worker, object: ObjectReference, _pin| {
             debug_assert!(
-                mmtk::memory_manager::is_mmtk_object(object.to_address::<Ruby>()),
+                mmtk::memory_manager::is_mmtk_object(object.to_address::<Ruby>()).is_some(),
                 "{} is not an MMTk object",
                 object
             );