diff --git a/Cargo.lock b/Cargo.lock
index deb6efd0..0c3df643 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -14,15 +14,6 @@ version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "41ed9a86bf92ae6580e0a31281f65a1b1d867c0cc68d5346e2ae128dddfa6a7d"
 
-[[package]]
-name = "atomic-polyfill"
-version = "1.0.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d299f547288d6db8d5c3a2916f7b2f66134b15b8c1ac1c4357dd3b8752af7bb2"
-dependencies = [
- "critical-section",
-]
-
 [[package]]
 name = "autocfg"
 version = "1.1.0"
@@ -702,12 +693,12 @@ dependencies = [
 
 [[package]]
 name = "once_cell"
-version = "1.18.0"
+version = "1.19.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dd8b5dd2ae5ed71462c540258bedcb51965123ad7e7ccf4b9a8cafaa4a63576d"
+checksum = "3fdb12b2476b595f9358c5161aa467c2438859caa136dec86c26fdd2efe17b92"
 dependencies = [
- "atomic-polyfill",
  "critical-section",
+ "portable-atomic",
 ]
 
 [[package]]
@@ -837,6 +828,12 @@ dependencies = [
  "plotters-backend",
 ]
 
+[[package]]
+name = "portable-atomic"
+version = "1.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7170ef9988bc169ba16dd36a7fa041e5c4cbeb6a35b76d4c03daded371eae7c0"
+
 [[package]]
 name = "ppv-lite86"
 version = "0.2.17"
diff --git a/k256/Cargo.toml b/k256/Cargo.toml
index 45bf0697..b9b55d4a 100644
--- a/k256/Cargo.toml
+++ b/k256/Cargo.toml
@@ -22,7 +22,7 @@ cfg-if = "1.0"
 elliptic-curve = { version = "0.13.8", default-features = false, features = ["hazmat", "sec1"] }
 
 # optional dependencies
-once_cell = { version = "1.18", optional = true, default-features = false }
+once_cell = { version = "1.19", optional = true, default-features = false }
 ecdsa-core = { version = "0.16.8", package = "ecdsa", optional = true, default-features = false, features = ["der"] }
 hex-literal = { version = "0.4", optional = true }
 serdect = { version = "0.2", optional = true, default-features = false }