diff --git a/.github/workflows/build-docs.yml b/.github/workflows/build-docs.yml
index cd572bbd..84a01a76 100644
--- a/.github/workflows/build-docs.yml
+++ b/.github/workflows/build-docs.yml
@@ -26,7 +26,7 @@ jobs:
 
       - uses: oxidize-rb/actions/setup-ruby-and-rust@v1
         with:
-          ruby-version: "3.4"
+          ruby-version: "4.0"
           rustup-toolchain: "${{ env.NIGHTLY_VERSION }}"
           bundler-cache: true
           cargo-cache: true
diff --git a/.github/workflows/build-gems.yml b/.github/workflows/build-gems.yml
index b117a0b6..f97df94b 100644
--- a/.github/workflows/build-gems.yml
+++ b/.github/workflows/build-gems.yml
@@ -42,7 +42,7 @@ jobs:
 
       - uses: ruby/setup-ruby@v1
         with:
-          ruby-version: "3.4"
+          ruby-version: "4.0"
 
       - uses: oxidize-rb/actions/cross-gem@v1
         id: cross-gem
@@ -66,7 +66,7 @@ jobs:
     strategy:
       matrix:
         os: ["ubuntu-latest"]
-        ruby: ["3.4"]
+        ruby: ["4.0"]
     steps:
       - uses: actions/checkout@v6
 
diff --git a/.github/workflows/memcheck.yml b/.github/workflows/memcheck.yml
index 66c769d7..af9e6eb3 100644
--- a/.github/workflows/memcheck.yml
+++ b/.github/workflows/memcheck.yml
@@ -7,10 +7,11 @@ on:
       ruby-version:
         description: "Ruby version to memcheck"
         required: true
-        default: "3.4"
+        default: "4.0"
         type: choice
         options:
           - "head"
+          - "4.0"
           - "3.4"
           - "3.3"
           - "3.2"
@@ -38,7 +39,7 @@ jobs:
 
       - uses: oxidize-rb/actions/setup-ruby-and-rust@v1
         with:
-          ruby-version: ${{ inputs.ruby-version || '3.4' }}
+          ruby-version: ${{ inputs.ruby-version || '4.0' }}
           bundler-cache: true
           cargo-cache: true
           cache-version: v2
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index e53a7c96..b5e19d40 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -42,7 +42,7 @@ jobs:
 
       - uses: ruby/setup-ruby@v1
         with:
-          ruby-version: "3.4"
+          ruby-version: "4.0"
 
       - uses: oxidize-rb/actions/cross-gem@v1
         id: cross-gem
@@ -73,7 +73,7 @@ jobs:
 
       - uses: oxidize-rb/actions/setup-ruby-and-rust@v1
         with:
-          ruby-version: "3.4"
+          ruby-version: "4.0"
           bundler-cache: true
           cargo-cache: true
           cache-version: v1
diff --git a/Cargo.lock b/Cargo.lock
index f7725338..8c32edc6 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1415,18 +1415,18 @@ dependencies = [
 
 [[package]]
 name = "rb-sys"
-version = "0.9.119"
+version = "0.9.124"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4519fc8de033923105f512c504a8f27714ef38648ccc30969362194c50b2ed08"
+checksum = "c85c4188462601e2aa1469def389c17228566f82ea72f137ed096f21591bc489"
 dependencies = [
  "rb-sys-build",
 ]
 
 [[package]]
 name = "rb-sys-build"
-version = "0.9.119"
+version = "0.9.124"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2e0109499e06c85f56df4abad7d9c642ea8a2dd821d1d7132b4d1b69534677f3"
+checksum = "568068db4102230882e6d4ae8de6632e224ca75fe5970f6e026a04e91ed635d3"
 dependencies = [
  "bindgen",
  "lazy_static",
diff --git a/Gemfile.lock b/Gemfile.lock
index 42ca8beb..4e52a07d 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -2,7 +2,7 @@ PATH
   remote: .
   specs:
     wasmtime (39.0.1)
-      rb_sys (~> 0.9.119)
+      rb_sys (~> 0.9.124)
 
 GEM
   remote: https://rubygems.org/
@@ -11,17 +11,17 @@ GEM
     benchmark-ips (2.14.0)
     bigdecimal (3.1.9)
     diff-lcs (1.6.2)
-    ffi (1.17.1)
-    ffi (1.17.1-aarch64-linux-gnu)
-    ffi (1.17.1-aarch64-linux-musl)
-    ffi (1.17.1-arm-linux-gnu)
-    ffi (1.17.1-arm-linux-musl)
-    ffi (1.17.1-arm64-darwin)
-    ffi (1.17.1-x86-linux-gnu)
-    ffi (1.17.1-x86-linux-musl)
-    ffi (1.17.1-x86_64-darwin)
-    ffi (1.17.1-x86_64-linux-gnu)
-    ffi (1.17.1-x86_64-linux-musl)
+    ffi (1.17.3)
+    ffi (1.17.3-aarch64-linux-gnu)
+    ffi (1.17.3-aarch64-linux-musl)
+    ffi (1.17.3-arm-linux-gnu)
+    ffi (1.17.3-arm-linux-musl)
+    ffi (1.17.3-arm64-darwin)
+    ffi (1.17.3-x86-linux-gnu)
+    ffi (1.17.3-x86-linux-musl)
+    ffi (1.17.3-x86_64-darwin)
+    ffi (1.17.3-x86_64-linux-gnu)
+    ffi (1.17.3-x86_64-linux-musl)
     fiddle (1.1.8)
     get_process_mem (1.0.0)
       bigdecimal (>= 2.0)
@@ -40,9 +40,9 @@ GEM
     rake (13.3.1)
     rake-compiler (1.3.0)
       rake
-    rake-compiler-dock (1.10.0)
-    rb_sys (0.9.119)
-      rake-compiler-dock (= 1.10.0)
+    rake-compiler-dock (1.11.0)
+    rb_sys (0.9.124)
+      rake-compiler-dock (= 1.11.0)
     regexp_parser (2.11.3)
     rspec (3.13.2)
       rspec-core (~> 3.13.0)
@@ -92,7 +92,7 @@ GEM
       prettier_print (>= 1.2.0)
     unicode-display_width (3.2.0)
       unicode-emoji (~> 4.1)
-    unicode-emoji (4.1.0)
+    unicode-emoji (4.2.0)
     yard (0.9.37)
     yard-rustdoc (0.4.2)
       syntax_tree (~> 6.0)
diff --git a/ext/src/helpers/tmplock.rs b/ext/src/helpers/tmplock.rs
index 5d6a5c6f..301c959b 100644
--- a/ext/src/helpers/tmplock.rs
+++ b/ext/src/helpers/tmplock.rs
@@ -1,11 +1,12 @@
 use magnus::{
     rb_sys::{protect, AsRawValue},
+    value::ReprValue,
     RString,
 };
 
 pub trait Tmplock {
-    fn as_locked_slice(&self) -> Result<(&[u8], TmplockGuard), magnus::Error>;
-    fn as_locked_str(&self) -> Result<(&str, TmplockGuard), magnus::Error>;
+    fn as_locked_slice(&self) -> Result<(&[u8], Option<TmplockGuard>), magnus::Error>;
+    fn as_locked_str(&self) -> Result<(&str, Option<TmplockGuard>), magnus::Error>;
 }
 
 #[derive(Debug)]
@@ -25,20 +26,28 @@ impl Drop for TmplockGuard {
 }
 
 impl Tmplock for RString {
-    fn as_locked_slice(&self) -> Result<(&[u8], TmplockGuard), magnus::Error> {
+    fn as_locked_slice(&self) -> Result<(&[u8], Option<TmplockGuard>), magnus::Error> {
         let raw = self.as_raw();
         let slice = unsafe { self.as_slice() };
-        let raw = protect(|| unsafe { rb_sys::rb_str_locktmp(raw) })?;
-        let guard = TmplockGuard { raw };
+        let guard = if self.is_frozen() {
+            None
+        } else {
+            let raw = protect(|| unsafe { rb_sys::rb_str_locktmp(raw) })?;
+            Some(TmplockGuard { raw })
+        };
 
         Ok((slice, guard))
     }
 
-    fn as_locked_str(&self) -> Result<(&str, TmplockGuard), magnus::Error> {
+    fn as_locked_str(&self) -> Result<(&str, Option<TmplockGuard>), magnus::Error> {
         let str_result = unsafe { self.as_str()? };
-        let raw = self.as_raw();
-        let raw = protect(|| unsafe { rb_sys::rb_str_locktmp(raw) })?;
-        let guard = TmplockGuard { raw };
+        let guard = if self.is_frozen() {
+            None
+        } else {
+            let raw = self.as_raw();
+            let raw = protect(|| unsafe { rb_sys::rb_str_locktmp(raw) })?;
+            Some(TmplockGuard { raw })
+        };
 
         Ok((str_result, guard))
     }
diff --git a/spec/integration/ractor_spec.rb b/spec/integration/ractor_spec.rb
index 5ae9b5e0..e61727c6 100644
--- a/spec/integration/ractor_spec.rb
+++ b/spec/integration/ractor_spec.rb
@@ -21,7 +21,7 @@
       Wasmtime::Instance.new(store, mod).invoke("hello")
     end
 
-    result = r.take
+    result = value(r)
     expect(result).to eq([1, 2, 3.0, 4.0])
   end
 
@@ -42,7 +42,13 @@
     end
 
     ractors.each do |ractor|
-      expect(ractor.take).to eq([1, 2, 3.0, 4.0])
+      expect(value(ractor)).to eq([1, 2, 3.0, 4.0])
     end
   end
+
+  if Gem::Version.new(RUBY_VERSION) >= Gem::Version.new("4.0")
+    def value(ractor) = ractor.value
+  else
+    def value(ractor) = ractor.take
+  end
 end
diff --git a/wasmtime.gemspec b/wasmtime.gemspec
index 60336019..28b4b9bb 100644
--- a/wasmtime.gemspec
+++ b/wasmtime.gemspec
@@ -29,5 +29,5 @@ Gem::Specification.new do |spec|
 
   spec.rdoc_options += ["--exclude", "vendor"]
 
-  spec.add_dependency "rb_sys", "~> 0.9.119"
+  spec.add_dependency "rb_sys", "~> 0.9.124"
 end