diff --git a/gc/mmtk/Cargo.lock b/gc/mmtk/Cargo.lock
index 4abd431f5e..b8a4584a37 100644
--- a/gc/mmtk/Cargo.lock
+++ b/gc/mmtk/Cargo.lock
@@ -432,7 +432,7 @@ dependencies = [
 [[package]]
 name = "mmtk"
 version = "0.30.0"
-source = "git+https://github.com/mmtk/mmtk-core.git?rev=68bf1b638263b250b12e55ef25bf8d09b01ca0b0#68bf1b638263b250b12e55ef25bf8d09b01ca0b0"
+source = "git+https://github.com/mmtk/mmtk-core.git?rev=2f6f078b6fd7bdc23688ead55a055d825a23b863#2f6f078b6fd7bdc23688ead55a055d825a23b863"
 dependencies = [
  "atomic",
  "atomic-traits",
@@ -468,7 +468,7 @@ dependencies = [
 [[package]]
 name = "mmtk-macros"
 version = "0.30.0"
-source = "git+https://github.com/mmtk/mmtk-core.git?rev=68bf1b638263b250b12e55ef25bf8d09b01ca0b0#68bf1b638263b250b12e55ef25bf8d09b01ca0b0"
+source = "git+https://github.com/mmtk/mmtk-core.git?rev=2f6f078b6fd7bdc23688ead55a055d825a23b863#2f6f078b6fd7bdc23688ead55a055d825a23b863"
 dependencies = [
  "proc-macro-error",
  "proc-macro2",
diff --git a/gc/mmtk/Cargo.toml b/gc/mmtk/Cargo.toml
index 93ad269a1a..05607538cb 100644
--- a/gc/mmtk/Cargo.toml
+++ b/gc/mmtk/Cargo.toml
@@ -26,7 +26,7 @@ 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 = "68bf1b638263b250b12e55ef25bf8d09b01ca0b0"
+rev = "2f6f078b6fd7bdc23688ead55a055d825a23b863"
 
 # Uncomment the following line to use mmtk-core from a local repository.
 # path = "../../../mmtk-core"