diff --git a/Cargo.lock b/Cargo.lock
index c9726d4..54354b7 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2,7 +2,7 @@
 # It is not intended for manual editing.
 [[package]]
 name = "bdwgc-alloc"
-version = "0.1.1"
+version = "0.2.0"
 dependencies = [
  "libc 0.2.51 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
diff --git a/Cargo.toml b/Cargo.toml
index 3a621b3..66240e8 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "bdwgc-alloc"
 description = "impl GlobalAlloc for bdwgc"
-version = "0.1.1"
+version = "0.2.0"
 authors = ["swgillespie <sean.william.g@gmail.com>", "Yota Toyama <raviqqe@gmail.com>"]
 repository = "https://github.com/raviqqe/bdwgc-rs"
 edition = "2018"
diff --git a/examples/allocation_loop/Cargo.lock b/examples/allocation_loop/Cargo.lock
index 45c13c6..1283123 100644
--- a/examples/allocation_loop/Cargo.lock
+++ b/examples/allocation_loop/Cargo.lock
@@ -4,12 +4,12 @@
 name = "allocation_loop"
 version = "0.1.0"
 dependencies = [
- "bdwgc-alloc 0.1.1",
+ "bdwgc-alloc 0.2.0",
 ]
 
 [[package]]
 name = "bdwgc-alloc"
-version = "0.1.1"
+version = "0.2.0"
 dependencies = [
  "libc 0.2.51 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
diff --git a/examples/dynamic_threads/Cargo.lock b/examples/dynamic_threads/Cargo.lock
index 8b6e754..73a095d 100644
--- a/examples/dynamic_threads/Cargo.lock
+++ b/examples/dynamic_threads/Cargo.lock
@@ -2,7 +2,7 @@
 # It is not intended for manual editing.
 [[package]]
 name = "bdwgc-alloc"
-version = "0.1.1"
+version = "0.2.0"
 dependencies = [
  "libc 0.2.51 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -11,7 +11,7 @@ dependencies = [
 name = "dynamic_threads"
 version = "0.1.0"
 dependencies = [
- "bdwgc-alloc 0.1.1",
+ "bdwgc-alloc 0.2.0",
 ]
 
 [[package]]
diff --git a/examples/dynamic_threads/src/main.rs b/examples/dynamic_threads/src/main.rs
index d436922..6e63a53 100644
--- a/examples/dynamic_threads/src/main.rs
+++ b/examples/dynamic_threads/src/main.rs
@@ -11,7 +11,7 @@ fn main() {
 
     loop {
         let handle = std::thread::spawn(move || {
-            Allocator::register_current_thread().unwrap();
+            unsafe { Allocator::register_current_thread().unwrap() }
 
             let mut _n =
                 unsafe { GLOBAL_ALLOCATOR.alloc(Layout::from_size_align(2 ^ 8, 8).unwrap()) };
@@ -20,7 +20,7 @@ fn main() {
                 _n = unsafe { GLOBAL_ALLOCATOR.alloc(Layout::from_size_align(2 ^ 8, 8).unwrap()) }
             }
 
-            Allocator::unregister_current_thread();
+            unsafe { Allocator::unregister_current_thread() }
         });
 
         handle.join().unwrap();
diff --git a/examples/static_threads/Cargo.lock b/examples/static_threads/Cargo.lock
index 1c2d41c..4e837af 100644
--- a/examples/static_threads/Cargo.lock
+++ b/examples/static_threads/Cargo.lock
@@ -2,7 +2,7 @@
 # It is not intended for manual editing.
 [[package]]
 name = "bdwgc-alloc"
-version = "0.1.1"
+version = "0.2.0"
 dependencies = [
  "libc 0.2.51 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -16,7 +16,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 name = "static_threads"
 version = "0.1.0"
 dependencies = [
- "bdwgc-alloc 0.1.1",
+ "bdwgc-alloc 0.2.0",
 ]
 
 [metadata]
diff --git a/examples/static_threads/src/main.rs b/examples/static_threads/src/main.rs
index 7ecd79b..da331f2 100644
--- a/examples/static_threads/src/main.rs
+++ b/examples/static_threads/src/main.rs
@@ -10,7 +10,7 @@ fn main() {
     unsafe { Allocator::initialize() }
 
     let handle = std::thread::spawn(move || {
-        Allocator::register_current_thread().unwrap();
+        unsafe { Allocator::register_current_thread().unwrap() }
 
         let mut _n = unsafe { GLOBAL_ALLOCATOR.alloc(Layout::from_size_align(2 ^ 8, 8).unwrap()) };
 
diff --git a/src/lib.rs b/src/lib.rs
index baf303b..4105b3d 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -32,23 +32,23 @@ impl Allocator {
         GC_allow_register_threads();
     }
 
-    pub fn register_current_thread() -> Result<(), error::Error> {
+    pub unsafe fn register_current_thread() -> Result<(), error::Error> {
         let mut base = GcStackBase {
             mem_base: std::ptr::null(),
             reg_base: std::ptr::null(),
         };
 
-        if unsafe { GC_get_stack_base(&mut base) } != GC_SUCCESS {
+        if GC_get_stack_base(&mut base) != GC_SUCCESS {
             return Err(error::Error::new("failed to get stack base"));
-        } else if unsafe { GC_register_my_thread(&base) } != GC_SUCCESS {
+        } else if GC_register_my_thread(&base) != GC_SUCCESS {
             return Err(error::Error::new("failed to register a thread for GC"));
         }
 
         Ok(())
     }
 
-    pub fn unregister_current_thread() {
-        unsafe { GC_unregister_my_thread() }
+    pub unsafe fn unregister_current_thread() {
+        GC_unregister_my_thread()
     }
 }