diff --git a/.github/workflows/argon2.yml b/.github/workflows/argon2.yml
index 75e3cfb5..164529d4 100644
--- a/.github/workflows/argon2.yml
+++ b/.github/workflows/argon2.yml
@@ -17,36 +17,35 @@ env:
   RUSTFLAGS: "-Dwarnings"
 
 jobs:
-# TODO(tarcieri): test when new cargo resolver is available (RFC 2957)
-#  build:
-#    runs-on: ubuntu-latest
-#    strategy:
-#      matrix:
-#        rust:
-#          - 1.47.0 # MSRV
-#          - stable
-#        target:
-#          - thumbv7em-none-eabi
-#          - wasm32-unknown-unknown
-#    steps:
-#      - uses: actions/checkout@v1
-#      - uses: actions-rs/toolchain@v1
-#        with:
-#          profile: minimal
-#          toolchain: ${{ matrix.rust }}
-#          target: ${{ matrix.target }}
-#          override: true
-#      - run: cargo build --target ${{ matrix.target }} --release --no-default-features
-#      - run: cargo build --target ${{ matrix.target }} --release --no-default-features --features password-hash
-#      - run: cargo build --target ${{ matrix.target }} --release
-#      - run: cargo build --target ${{ matrix.target }} --release --features zeroize
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        rust:
+          - 1.51.0 # MSRV
+          - stable
+        target:
+          - thumbv7em-none-eabi
+          - wasm32-unknown-unknown
+    steps:
+      - uses: actions/checkout@v1
+      - uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: ${{ matrix.rust }}
+          target: ${{ matrix.target }}
+          override: true
+      - run: cargo build --target ${{ matrix.target }} --release --no-default-features
+      - run: cargo build --target ${{ matrix.target }} --release --no-default-features --features password-hash
+      - run: cargo build --target ${{ matrix.target }} --release
+      - run: cargo build --target ${{ matrix.target }} --release --features zeroize
 
   test:
     runs-on: ubuntu-latest
     strategy:
       matrix:
         rust:
-          - 1.47.0 # MSRV
+          - 1.51.0 # MSRV
           - stable
     steps:
       - uses: actions/checkout@v1
diff --git a/.github/workflows/bcrypt-pbkdf.yml b/.github/workflows/bcrypt-pbkdf.yml
index 30e41b5b..196272e9 100644
--- a/.github/workflows/bcrypt-pbkdf.yml
+++ b/.github/workflows/bcrypt-pbkdf.yml
@@ -22,7 +22,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - 1.47.0 # MSRV
+          - 1.51.0 # MSRV
           - stable
         target:
           - thumbv7em-none-eabi
@@ -42,7 +42,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - 1.47.0 # MSRV
+          - 1.51.0 # MSRV
           - stable
     steps:
       - uses: actions/checkout@v1
diff --git a/.github/workflows/pbkdf2.yml b/.github/workflows/pbkdf2.yml
index 3674d3a0..e6430e13 100644
--- a/.github/workflows/pbkdf2.yml
+++ b/.github/workflows/pbkdf2.yml
@@ -17,33 +17,32 @@ env:
   RUSTFLAGS: "-Dwarnings"
 
 jobs:
-# TODO(tarcieri): test when new cargo resolver is available (RFC 2957)
-#  build:
-#    runs-on: ubuntu-latest
-#    strategy:
-#      matrix:
-#        rust:
-#          - 1.47.0 # MSRV
-#          - stable
-#        target:
-#          - thumbv7em-none-eabi
-#          - wasm32-unknown-unknown
-#    steps:
-#      - uses: actions/checkout@v1
-#      - uses: actions-rs/toolchain@v1
-#        with:
-#          profile: minimal
-#          toolchain: ${{ matrix.rust }}
-#          target: ${{ matrix.target }}
-#          override: true
-#      - run: cargo build --target ${{ matrix.target }} --release --no-default-features
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        rust:
+          - 1.51.0 # MSRV
+          - stable
+        target:
+          - thumbv7em-none-eabi
+          - wasm32-unknown-unknown
+    steps:
+      - uses: actions/checkout@v1
+      - uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: ${{ matrix.rust }}
+          target: ${{ matrix.target }}
+          override: true
+      - run: cargo build --target ${{ matrix.target }} --release --no-default-features
 
   test:
     runs-on: ubuntu-latest
     strategy:
       matrix:
         rust:
-          - 1.47.0 # MSRV
+          - 1.51.0 # MSRV
           - stable
     steps:
       - uses: actions/checkout@v1
diff --git a/.github/workflows/scrypt.yml b/.github/workflows/scrypt.yml
index 8365b636..8ed510bb 100644
--- a/.github/workflows/scrypt.yml
+++ b/.github/workflows/scrypt.yml
@@ -17,34 +17,33 @@ env:
   RUSTFLAGS: "-Dwarnings"
 
 jobs:
-# TODO(tarcieri): test when new cargo resolver is available (RFC 2957)
-#  build:
-#    runs-on: ubuntu-latest
-#    strategy:
-#      matrix:
-#        rust:
-#          - 1.47.0 # MSRV
-#          - stable
-#        target:
-#          - thumbv7em-none-eabi
-#          - wasm32-unknown-unknown
-#    steps:
-#      - uses: actions/checkout@v1
-#      - uses: actions-rs/toolchain@v1
-#        with:
-#          profile: minimal
-#          toolchain: ${{ matrix.rust }}
-#          target: ${{ matrix.target }}
-#          override: true
-#      - run: cargo build --target ${{ matrix.target }} --release --no-default-features
-#      - run: cargo build --target ${{ matrix.target }} --release --no-default-features --features simple
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        rust:
+          - 1.51.0 # MSRV
+          - stable
+        target:
+          - thumbv7em-none-eabi
+          - wasm32-unknown-unknown
+    steps:
+      - uses: actions/checkout@v1
+      - uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: ${{ matrix.rust }}
+          target: ${{ matrix.target }}
+          override: true
+      - run: cargo build --target ${{ matrix.target }} --release --no-default-features
+      - run: cargo build --target ${{ matrix.target }} --release --no-default-features --features simple
 
   test:
     runs-on: ubuntu-latest
     strategy:
       matrix:
         rust:
-          - 1.47.0 # MSRV
+          - 1.51.0 # MSRV
           - stable
     steps:
       - uses: actions/checkout@v1
diff --git a/.github/workflows/sha-crypt.yml b/.github/workflows/sha-crypt.yml
index ad5b867c..4afade82 100644
--- a/.github/workflows/sha-crypt.yml
+++ b/.github/workflows/sha-crypt.yml
@@ -22,7 +22,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - 1.47.0 # MSRV
+          - 1.51.0 # MSRV
           - stable
         target:
           - thumbv7em-none-eabi
@@ -42,7 +42,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - 1.47.0 # MSRV
+          - 1.51.0 # MSRV
           - stable
     steps:
       - uses: actions/checkout@v1
diff --git a/.github/workflows/workspace.yml b/.github/workflows/workspace.yml
index d91f1050..90c59925 100644
--- a/.github/workflows/workspace.yml
+++ b/.github/workflows/workspace.yml
@@ -16,7 +16,7 @@ jobs:
       - uses: actions/checkout@v1
       - uses: actions-rs/toolchain@v1
         with:
-          toolchain: 1.47.0 # MSRV
+          toolchain: 1.51.0 # MSRV
           components: clippy
           override: true
           profile: minimal
diff --git a/Cargo.lock b/Cargo.lock
index 93e4e7f4..92f8ede5 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -31,7 +31,7 @@ name = "bcrypt-pbkdf"
 version = "0.6.2"
 dependencies = [
  "blowfish",
- "crypto-mac 0.11.1",
+ "crypto-mac 0.11.0",
  "pbkdf2",
  "sha2",
  "zeroize",
@@ -161,9 +161,9 @@ dependencies = [
 
 [[package]]
 name = "crypto-mac"
-version = "0.11.1"
+version = "0.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b1d1a86f49236c215f271d40892d5fc950490551400b02ef360692c29815c714"
+checksum = "25fab6889090c8133f3deb8f73ba3c65a7f456f66436fc012a1b1e272b1e103e"
 dependencies = [
  "generic-array",
  "subtle",
@@ -226,7 +226,7 @@ version = "0.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2a2a2320eb7ec0ebe8da8f744d7812d9fc4cb4d09344ac01898dbcb6a20ae69b"
 dependencies = [
- "crypto-mac 0.11.1",
+ "crypto-mac 0.11.0",
  "digest",
 ]
 
@@ -282,7 +282,7 @@ dependencies = [
 name = "pbkdf2"
 version = "0.8.0"
 dependencies = [
- "crypto-mac 0.11.1",
+ "crypto-mac 0.11.0",
  "hex-literal",
  "hmac",
  "password-hash",
@@ -437,9 +437,9 @@ dependencies = [
 
 [[package]]
 name = "subtle"
-version = "2.4.1"
+version = "2.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6bdef32e8150c2a081110b42772ffe7d7c9032b606bc226c8260fd97e0976601"
+checksum = "343f3f510c2915908f155e94f17220b19ccfacf2a64a2a5d8004f2c3e311e7fd"
 
 [[package]]
 name = "typenum"
diff --git a/Cargo.toml b/Cargo.toml
index 1f251097..5ba2730f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,4 +1,5 @@
 [workspace]
+resolver = "2"
 members = [
     "argon2",
     "bcrypt-pbkdf",
diff --git a/argon2/Cargo.toml b/argon2/Cargo.toml
index bf82418f..4abb5fb9 100644
--- a/argon2/Cargo.toml
+++ b/argon2/Cargo.toml
@@ -19,7 +19,7 @@ base64ct = "1"
 blake2 = { version = "0.9", default-features = false }
 password-hash = { version = "0.3", optional = true }
 rayon = { version = "1", optional = true }
-zeroize = { version = ">=1, <1.4", optional = true }
+zeroize = { version = ">=1, <1.5", optional = true }
 
 [dev-dependencies]
 hex-literal = "0.3"
diff --git a/argon2/README.md b/argon2/README.md
index d7bc6e8d..3c064a61 100644
--- a/argon2/README.md
+++ b/argon2/README.md
@@ -13,7 +13,7 @@ Pure Rust implementation of the [Argon2] password hashing function.
 
 ## Minimum Supported Rust Version
 
-Rust **1.47** or higher.
+Rust **1.51** or higher.
 
 Minimum supported Rust version can be changed in the future, but it will be
 done with a minor version bump.
@@ -45,7 +45,7 @@ dual licensed as above, without any additional terms or conditions.
 [docs-image]: https://docs.rs/argon2/badge.svg
 [docs-link]: https://docs.rs/argon2/
 [license-image]: https://img.shields.io/badge/license-Apache2.0/MIT-blue.svg
-[rustc-image]: https://img.shields.io/badge/rustc-1.47+-blue.svg
+[rustc-image]: https://img.shields.io/badge/rustc-1.51+-blue.svg
 [chat-image]: https://img.shields.io/badge/zulip-join_chat-blue.svg
 [chat-link]: https://rustcrypto.zulipchat.com/#narrow/stream/260046-password-hashes
 [build-image]: https://github.com/RustCrypto/password-hashes/workflows/argon2/badge.svg?branch=master&event=push
diff --git a/bcrypt-pbkdf/Cargo.toml b/bcrypt-pbkdf/Cargo.toml
index 0bf4132c..84bd816e 100644
--- a/bcrypt-pbkdf/Cargo.toml
+++ b/bcrypt-pbkdf/Cargo.toml
@@ -15,7 +15,7 @@ blowfish = { version = "0.8", features = ["bcrypt"] }
 crypto-mac = "0.11"
 pbkdf2 = { version = "0.8", default-features = false, path = "../pbkdf2" }
 sha2 = { version = "0.9", default-features = false }
-zeroize = { version = ">=1, <1.4", default-features = false }
+zeroize = { version = ">=1, <1.5", default-features = false }
 
 [features]
 default = ["std"]
diff --git a/pbkdf2/README.md b/pbkdf2/README.md
index 2d5a2c78..0127a1b7 100644
--- a/pbkdf2/README.md
+++ b/pbkdf2/README.md
@@ -13,7 +13,7 @@ Pure Rust implementation of the [Password-Based Key Derivation Function v2 (PBKD
 
 ## Minimum Supported Rust Version
 
-Rust **1.47** or higher.
+Rust **1.51** or higher.
 
 Minimum supported Rust version can be changed in the future, but it will be
 done with a minor version bump.
@@ -45,7 +45,7 @@ dual licensed as above, without any additional terms or conditions.
 [docs-image]: https://docs.rs/pbkdf2/badge.svg
 [docs-link]: https://docs.rs/pbkdf2/
 [license-image]: https://img.shields.io/badge/license-Apache2.0/MIT-blue.svg
-[rustc-image]: https://img.shields.io/badge/rustc-1.47+-blue.svg
+[rustc-image]: https://img.shields.io/badge/rustc-1.51+-blue.svg
 [chat-image]: https://img.shields.io/badge/zulip-join_chat-blue.svg
 [chat-link]: https://rustcrypto.zulipchat.com/#narrow/stream/260046-password-hashes
 [build-image]: https://github.com/RustCrypto/password-hashes/workflows/pbkdf2/badge.svg?branch=master&event=push
diff --git a/scrypt/README.md b/scrypt/README.md
index 3bf721b9..7c807fa7 100644
--- a/scrypt/README.md
+++ b/scrypt/README.md
@@ -13,7 +13,7 @@ Pure Rust implementation of the [scrypt key derivation function][1].
 
 ## Minimum Supported Rust Version
 
-Rust **1.47** or higher.
+Rust **1.51** or higher.
 
 Minimum supported Rust version can be changed in the future, but it will be
 done with a minor version bump.
@@ -45,7 +45,7 @@ dual licensed as above, without any additional terms or conditions.
 [docs-image]: https://docs.rs/scrypt/badge.svg
 [docs-link]: https://docs.rs/scrypt/
 [license-image]: https://img.shields.io/badge/license-Apache2.0/MIT-blue.svg
-[rustc-image]: https://img.shields.io/badge/rustc-1.47+-blue.svg
+[rustc-image]: https://img.shields.io/badge/rustc-1.51+-blue.svg
 [chat-image]: https://img.shields.io/badge/zulip-join_chat-blue.svg
 [chat-link]: https://rustcrypto.zulipchat.com/#narrow/stream/260046-password-hashes
 [build-image]: https://github.com/RustCrypto/password-hashes/workflows/scrypt/badge.svg?branch=master&event=push
diff --git a/sha-crypt/Cargo.toml b/sha-crypt/Cargo.toml
index 603d5d56..44ef62ca 100644
--- a/sha-crypt/Cargo.toml
+++ b/sha-crypt/Cargo.toml
@@ -17,7 +17,7 @@ readme = "README.md"
 [dependencies]
 sha2 = { version = "0.9", default-features = false }
 rand = { version = "0.8", optional = true }
-subtle = { version = "=2.4", optional = true, default-features = false }
+subtle = { version = ">=2, <2.4", optional = true, default-features = false }
 
 [features]
 default = ["simple"]
diff --git a/sha-crypt/README.md b/sha-crypt/README.md
index 8997ce8e..86d10ace 100644
--- a/sha-crypt/README.md
+++ b/sha-crypt/README.md
@@ -17,7 +17,7 @@ Password hashes using this algorithm start with `$6$` when encoded using the
 
 ## Minimum Supported Rust Version
 
-Rust **1.41** or higher.
+Rust **1.51** or higher.
 
 Minimum supported Rust version can be changed in the future, but it will be
 done with a minor version bump.
@@ -49,7 +49,7 @@ dual licensed as above, without any additional terms or conditions.
 [docs-image]: https://docs.rs/sha-crypt/badge.svg
 [docs-link]: https://docs.rs/sha-crypt/
 [license-image]: https://img.shields.io/badge/license-Apache2.0/MIT-blue.svg
-[rustc-image]: https://img.shields.io/badge/rustc-1.47+-blue.svg
+[rustc-image]: https://img.shields.io/badge/rustc-1.51+-blue.svg
 [chat-image]: https://img.shields.io/badge/zulip-join_chat-blue.svg
 [chat-link]: https://rustcrypto.zulipchat.com/#narrow/stream/260046-password-hashes
 [build-image]: https://github.com/RustCrypto/password-hashes/workflows/sha-crypt/badge.svg?branch=master&event=push