diff --git a/shard.yml b/shard.yml
index 0978cfc..fa7c972 100644
--- a/shard.yml
+++ b/shard.yml
@@ -4,7 +4,7 @@ version: 1.1.0
 authors:
 - Andrew Hamon <andrew@hamon.cc>
 - Didactic Drunk <1479616+didactic-drunk@users.noreply.github.com>
-crystal: 0.29.0
+crystal: 0.31.1
 targets:
   pwhash_selector:
     main: examples/pwhash_selector.cr
diff --git a/src/sodium/cipher/chalsa.cr b/src/sodium/cipher/chalsa.cr
index 1c1cacd..eb46423 100644
--- a/src/sodium/cipher/chalsa.cr
+++ b/src/sodium/cipher/chalsa.cr
@@ -72,8 +72,8 @@ module Sodium::Cipher
     end
 
     abstract def update(src : Bytes, dst : Bytes)
-    abstract def key_size
-    abstract def nonce_size
+    abstract def key_size : Int32
+    abstract def nonce_size : Int32
   end
 
   {% for key, val in {"XSalsa20" => "xsalsa20", "Salsa20" => "salsa20", "XChaCha20" => "xchacha20", "ChaCha20Ietf" => "chacha20_ietf", "ChaCha20" => "chacha20"} %}
diff --git a/src/sodium/crypto_box/public_key.cr b/src/sodium/crypto_box/public_key.cr
index 0ce79a8..b93b7c8 100644
--- a/src/sodium/crypto_box/public_key.cr
+++ b/src/sodium/crypto_box/public_key.cr
@@ -7,7 +7,7 @@ class Sodium::CryptoBox
     SEAL_SIZE = LibSodium.crypto_box_sealbytes
 
     # Returns key
-    delegate to_slice, to: @bytes
+    delegate_to_slice to: @bytes
 
     # :nodoc:
     # Only used by SecretKey
diff --git a/src/sodium/crypto_box/secret_key.cr b/src/sodium/crypto_box/secret_key.cr
index ffbd753..c019ab5 100644
--- a/src/sodium/crypto_box/secret_key.cr
+++ b/src/sodium/crypto_box/secret_key.cr
@@ -42,7 +42,7 @@ class Sodium::CryptoBox
     getter public_key : PublicKey
 
     # Returns key
-    delegate to_slice, to: @sbuf
+    delegate_to_slice to: @sbuf
 
     @seed : SecureBuffer?
 
diff --git a/src/sodium/kdf.cr b/src/sodium/kdf.cr
index 806952d..c2112f4 100644
--- a/src/sodium/kdf.cr
+++ b/src/sodium/kdf.cr
@@ -23,7 +23,7 @@ module Sodium
     CONTEXT_SIZE = LibSodium.crypto_kdf_contextbytes
 
     # Returns key
-    delegate to_slice, to: @sbuf
+    delegate_to_slice to: @sbuf
 
     # Use an existing KDF key.
     #
diff --git a/src/sodium/lib_sodium.cr b/src/sodium/lib_sodium.cr
index b79ee2d..8e6e954 100644
--- a/src/sodium/lib_sodium.cr
+++ b/src/sodium/lib_sodium.cr
@@ -1,6 +1,12 @@
 require "random/secure"
 require "./error"
 
+macro delegate_to_slice(to object)
+  def to_slice() : Bytes
+    {{object.id}}.to_slice
+  end
+end
+
 module Sodium
   @[Link(ldflags: "`#{__DIR__}/../../build/pkg-libs.sh #{__DIR__}/../..`")]
   lib LibSodium
diff --git a/src/sodium/nonce.cr b/src/sodium/nonce.cr
index 9c045f0..4484ef1 100644
--- a/src/sodium/nonce.cr
+++ b/src/sodium/nonce.cr
@@ -16,7 +16,7 @@ module Sodium
     property? reusable = false
 
     # Returns bytes
-    delegate to_slice, to: @bytes
+    delegate_to_slice to: @bytes
 
     delegate bytesize, to: @bytes
 
diff --git a/src/sodium/secret_box.cr b/src/sodium/secret_box.cr
index c179e06..d22e37e 100644
--- a/src/sodium/secret_box.cr
+++ b/src/sodium/secret_box.cr
@@ -20,7 +20,7 @@ module Sodium
     MAC_SIZE   = LibSodium.crypto_secretbox_macbytes.to_i
 
     # Returns key
-    delegate to_slice, to: @key
+    delegate_to_slice to: @key
 
     # Encryption key
     getter key : SecureBuffer
diff --git a/src/sodium/sign/public_key.cr b/src/sodium/sign/public_key.cr
index f4eaedd..e89d584 100644
--- a/src/sodium/sign/public_key.cr
+++ b/src/sodium/sign/public_key.cr
@@ -6,7 +6,7 @@ module Sodium
     SIG_SIZE = LibSodium.crypto_sign_bytes.to_i
 
     # Returns key
-    delegate to_slice, to: @bytes
+    delegate_to_slice to: @bytes
 
     # :nodoc:
     # Only used by SecretKey
diff --git a/src/sodium/sign/secret_key.cr b/src/sodium/sign/secret_key.cr
index 8114d1e..86bb807 100644
--- a/src/sodium/sign/secret_key.cr
+++ b/src/sodium/sign/secret_key.cr
@@ -21,7 +21,7 @@ module Sodium
     getter public_key : PublicKey
 
     # Returns key
-    delegate to_slice, to: @sbuf
+    delegate_to_slice to: @sbuf
 
     @seed : SecureBuffer?