diff --git a/src/digest/io_digest.cr b/src/digest/io_digest.cr
index 06167a349870..0efcb56b7715 100644
--- a/src/digest/io_digest.cr
+++ b/src/digest/io_digest.cr
@@ -30,8 +30,8 @@ class IO::Digest < IO
   def initialize(@io : IO, @digest_algorithm : ::Digest, @mode = DigestMode::Read)
   end
 
-  def read(slice : Bytes)
-    read_bytes = io.read(slice)
+  def read(slice : Bytes) : Int32
+    read_bytes = io.read(slice).to_i32
     if @mode.read?
       digest_algorithm.update(slice[0, read_bytes])
     end
diff --git a/src/http/content.cr b/src/http/content.cr
index 2c4be03cb32e..9bec0e66abda 100644
--- a/src/http/content.cr
+++ b/src/http/content.cr
@@ -26,7 +26,7 @@ module HTTP
   class FixedLengthContent < IO::Sized
     include Content
 
-    def read(slice : Bytes)
+    def read(slice : Bytes) : Int32
       ensure_send_continue
       super
     end
@@ -58,9 +58,9 @@ module HTTP
     def initialize(@io : IO)
     end
 
-    def read(slice : Bytes)
+    def read(slice : Bytes) : Int32
       ensure_send_continue
-      @io.read(slice)
+      @io.read(slice).to_i32
     end
 
     def read_byte : UInt8?
@@ -112,7 +112,7 @@ module HTTP
       @received_final_chunk = false
     end
 
-    def read(slice : Bytes)
+    def read(slice : Bytes) : Int32
       ensure_send_continue
       count = slice.size
       return 0 if count == 0
@@ -123,7 +123,7 @@ module HTTP
 
       to_read = Math.min(count, @chunk_remaining)
 
-      bytes_read = @io.read slice[0, to_read]
+      bytes_read = @io.read(slice[0, to_read]).to_i32
 
       if bytes_read == 0
         raise IO::EOFError.new("Invalid HTTP chunked content")
diff --git a/src/io/argf.cr b/src/io/argf.cr
index 2874e7d16dca..afa92c2a545b 100644
--- a/src/io/argf.cr
+++ b/src/io/argf.cr
@@ -10,7 +10,7 @@ class IO::ARGF < IO
     @read_from_stdin = false
   end
 
-  def read(slice : Bytes)
+  def read(slice : Bytes) : Int32
     first_initialize unless @initialized
 
     if current_io = @current_io
diff --git a/src/io/hexdump.cr b/src/io/hexdump.cr
index b48d36ac8bfa..1ead92779cc0 100644
--- a/src/io/hexdump.cr
+++ b/src/io/hexdump.cr
@@ -26,8 +26,8 @@ class IO::Hexdump < IO
   def initialize(@io : IO, @output : IO = STDERR, @read = false, @write = false)
   end
 
-  def read(buf : Bytes)
-    @io.read(buf).tap do |read_bytes|
+  def read(buf : Bytes) : Int32
+    @io.read(buf).to_i32.tap do |read_bytes|
       buf[0, read_bytes].hexdump(@output) if @read && read_bytes
     end
   end
diff --git a/src/io/sized.cr b/src/io/sized.cr
index 6ad0a7da1b14..ad451523fffe 100644
--- a/src/io/sized.cr
+++ b/src/io/sized.cr
@@ -25,11 +25,11 @@ class IO::Sized < IO
     @read_remaining = read_size.to_u64
   end
 
-  def read(slice : Bytes)
+  def read(slice : Bytes) : Int32
     check_open
 
     count = {slice.size.to_u64, @read_remaining}.min
-    bytes_read = @io.read slice[0, count]
+    bytes_read = @io.read(slice[0, count]).to_i32
     @read_remaining -= bytes_read
     bytes_read
   end
diff --git a/src/io/stapled.cr b/src/io/stapled.cr
index 3fc6e2f92d7d..98d90eadb238 100644
--- a/src/io/stapled.cr
+++ b/src/io/stapled.cr
@@ -30,10 +30,10 @@ class IO::Stapled < IO
   end
 
   # Reads a slice from `reader`.
-  def read(slice : Bytes)
+  def read(slice : Bytes) : Int32
     check_open
 
-    @reader.read(slice)
+    @reader.read(slice).to_i32
   end
 
   # Gets a string from `reader`.