diff --git a/src/crypto-secret/stateful.cr b/src/crypto-secret/stateful.cr
index 036a724..c552645 100644
--- a/src/crypto-secret/stateful.cr
+++ b/src/crypto-secret/stateful.cr
@@ -30,7 +30,7 @@ module Crypto::Secret
 
     # Marks a region allocated as readable and writable
     # WARNING: Not thread safe
-    def readwrite
+    def readwrite : self
       raise Error::KeyWiped.new if @state == State::Wiped
       readwrite_impl
       @state = State::Readwrite
@@ -49,7 +49,7 @@ module Crypto::Secret
 
     # Marks a region allocated using sodium_malloc() or sodium_allocarray() as read-only.
     # WARNING: Not thread safe
-    def readonly
+    def readonly : self
       raise Error::KeyWiped.new if @state == State::Wiped
       readonly_impl
       @state = State::Readonly
@@ -58,7 +58,7 @@ module Crypto::Secret
 
     # Makes a region inaccessible. It cannot be read or written, but the data are preserved.
     # WARNING: Not thread safe
-    def noaccess
+    def noaccess : self
       raise Error::KeyWiped.new if @state == State::Wiped
       noaccess_impl
       @state = State::Noaccess
diff --git a/src/crypto-secret/stateless.cr b/src/crypto-secret/stateless.cr
index fdbae57..b71b8ac 100644
--- a/src/crypto-secret/stateless.cr
+++ b/src/crypto-secret/stateless.cr
@@ -11,7 +11,8 @@ module Crypto::Secret::Stateless
   end
 
   # Not thread safe
-  def readwrite
+  def readwrite : self
+    self
   end
 
   # Yields a Slice that is readable and writable
@@ -26,7 +27,8 @@ module Crypto::Secret::Stateless
   end
 
   # Not thread safe
-  def readonly
+  def readonly : self
+    self
   end
 
   # Yields a Slice that is readable possibly writable depending on the prior protection level and underlying implementation
@@ -40,7 +42,8 @@ module Crypto::Secret::Stateless
   end
 
   # Not thread safe
-  def noaccess
+  def noaccess : self
+    self
   end
 
   # Not thread safe