diff --git a/Cargo.lock b/Cargo.lock
index 447b8706d4..4aa990fcaa 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1187,6 +1187,11 @@ name = "hex"
 version = "0.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "hex"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "hex-literal"
 version = "0.2.1"
@@ -3417,7 +3422,7 @@ dependencies = [
 name = "solana-merkle-tree"
 version = "0.19.0-pre0"
 dependencies = [
- "hex 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "hex 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "solana-sdk 0.19.0-pre0",
 ]
 
@@ -3577,7 +3582,7 @@ dependencies = [
  "byteorder 1.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "chrono 0.4.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "generic-array 0.13.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "hex 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "hex 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "itertools 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "memmap 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -5305,6 +5310,7 @@ dependencies = [
 "checksum hashbrown 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)" = "3bae29b6653b3412c2e71e9d486db9f9df5d701941d86683005efb9f2d28e3da"
 "checksum heck 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "20564e78d53d2bb135c343b3f47714a56af2061f1c928fdb541dc7b9fdd94205"
 "checksum hex 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)" = "805026a5d0141ffc30abb3be3173848ad46a1b1664fe632428479619a3644d77"
+"checksum hex 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "023b39be39e3a2da62a94feb433e91e8bcd37676fbc8bea371daf52b7a769a3e"
 "checksum hex-literal 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "961de220ec9a91af2e1e5bd80d02109155695e516771762381ef8581317066e0"
 "checksum hex-literal-impl 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "06095d08c7c05760f11a071b3e1d4c5b723761c01bd8d7201c30a9536668a612"
 "checksum hex_fmt 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "b07f60793ff0a4d9cef0f18e63b5357e06209987153a64648c972c1e5aff336f"
diff --git a/merkle-tree/Cargo.toml b/merkle-tree/Cargo.toml
index 9ffe4c7c81..c03f3480f5 100644
--- a/merkle-tree/Cargo.toml
+++ b/merkle-tree/Cargo.toml
@@ -12,7 +12,7 @@ edition = "2018"
 solana-sdk = { path = "../sdk", version = "0.19.0-pre0" }
 
 [dev-dependencies]
-hex = "0.3.2"
+hex = "0.4.0"
 
 [lib]
 crate-type = ["lib"]
diff --git a/sdk/Cargo.toml b/sdk/Cargo.toml
index 23285afd59..6642b5b385 100644
--- a/sdk/Cargo.toml
+++ b/sdk/Cargo.toml
@@ -33,7 +33,7 @@ bs58 = "0.2.5"
 byteorder = { version = "1.3.2", optional = true }
 chrono = { version = "0.4.9", features = ["serde"], optional = true }
 generic-array = { version = "0.13.2", default-features = false, features = ["serde", "more_lengths"] }
-hex = "0.3.2"
+hex = "0.4.0"
 itertools = { version = "0.8.0" }
 log = { version = "0.4.8" }
 memmap = { version = "0.6.2", optional = true }