diff --git a/spec/std/io/io_spec.cr b/spec/std/io/io_spec.cr
index dfe944e98000..6c96c54d5b07 100644
--- a/spec/std/io/io_spec.cr
+++ b/spec/std/io/io_spec.cr
@@ -796,6 +796,19 @@ describe IO do
           io.encoding.should eq("UTF-8")
         end
 
+        it "handles long lines correctly with invalid: :skip" do
+          # Using both ASCII characters and a 26-byte Unicode characters to
+          # ensure we hit as many byte boundaries inside the Unicode characters
+          # as we can to get sufficient confidence in this test.
+          text = "test string 👩🏾‍🤝‍👨🏻" * 10240
+          io = IO::Memory.new
+          io.set_encoding "UTF-8", invalid: :skip
+          io << text
+
+          io.bytesize.should eq text.bytesize
+          io.to_slice.should eq text.to_slice
+        end
+
         it "does skips when converting to UTF-8" do
           io = SimpleIOMemory.new(Base64.decode_string("ey8qx+Tl8fwg7+Dw4Ozl8vD7IOLo5+jy4CovfQ=="))
           io.set_encoding("UTF-8", invalid: :skip)
diff --git a/src/crystal/iconv.cr b/src/crystal/iconv.cr
index 59fd9519c983..4a45b3876a5a 100644
--- a/src/crystal/iconv.cr
+++ b/src/crystal/iconv.cr
@@ -58,10 +58,20 @@ struct Crystal::Iconv
   def convert(inbuf : UInt8**, inbytesleft : LibC::SizeT*, outbuf : UInt8**, outbytesleft : LibC::SizeT*)
     {% if flag?(:freebsd) || flag?(:dragonfly) %}
       if @skip_invalid
-        return LibC.__iconv(@iconv, inbuf, inbytesleft, outbuf, outbytesleft, LibC::ICONV_F_HIDE_INVALID, out invalids)
+        err = LibC.__iconv(@iconv, inbuf, inbytesleft, outbuf, outbytesleft, LibC::ICONV_F_HIDE_INVALID, out invalids)
+        if err == ERROR && Errno.value != Errno::E2BIG
+          return err
+        else
+          return
+        end
       end
     {% end %}
-    {{ USE_LIBICONV ? LibIconv : LibC }}.iconv(@iconv, inbuf, inbytesleft, outbuf, outbytesleft)
+
+    err = {{ USE_LIBICONV ? LibIconv : LibC }}.iconv(@iconv, inbuf, inbytesleft, outbuf, outbytesleft)
+    if err == Crystal::Iconv::ERROR && Errno.value != Errno::E2BIG && Errno.value != Errno::EINVAL
+      handle_invalid(inbuf, inbytesleft)
+    end
+    err
   end
 
   def handle_invalid(inbuf, inbytesleft)
diff --git a/src/io/encoding.cr b/src/io/encoding.cr
index b741ea07e675..4cf57f413ef8 100644
--- a/src/io/encoding.cr
+++ b/src/io/encoding.cr
@@ -39,11 +39,11 @@ class IO
       while inbytesleft > 0
         outbuf_ptr = outbuf.to_unsafe
         outbytesleft = LibC::SizeT.new(outbuf.size)
-        err = @iconv.convert(pointerof(inbuf_ptr), pointerof(inbytesleft), pointerof(outbuf_ptr), pointerof(outbytesleft))
-        if err == Crystal::Iconv::ERROR
+        result = @iconv.convert(pointerof(inbuf_ptr), pointerof(inbytesleft), pointerof(outbuf_ptr), pointerof(outbytesleft))
+        io.write(outbuf.to_slice[0, outbuf.size - outbytesleft])
+        if result == Crystal::Iconv::ERROR && Errno.value == Errno::EINVAL
           @iconv.handle_invalid(pointerof(inbuf_ptr), pointerof(inbytesleft))
         end
-        io.write(outbuf.to_slice[0, outbuf.size - outbytesleft])
       end
     end
 
@@ -97,11 +97,7 @@ class IO
 
         # Check for errors
         if result == Crystal::Iconv::ERROR
-          case Errno.value
-          when Errno::EILSEQ
-            # For an illegal sequence we just skip one byte and we'll continue next
-            @iconv.handle_invalid(pointerof(@in_buffer), pointerof(@in_buffer_left))
-          when Errno::EINVAL
+          if Errno.value == Errno::EINVAL
             # EINVAL means "An incomplete multibyte sequence has been encountered in the input."
             old_in_buffer_left = @in_buffer_left
 
diff --git a/src/string.cr b/src/string.cr
index 940ba15f6602..7a527a8c2ec4 100644
--- a/src/string.cr
+++ b/src/string.cr
@@ -1823,7 +1823,7 @@ class String
         outbuf_ptr = outbuf.to_unsafe
         outbytesleft = LibC::SizeT.new(outbuf.size)
         err = iconv.convert(pointerof(inbuf_ptr), pointerof(inbytesleft), pointerof(outbuf_ptr), pointerof(outbytesleft))
-        if err == Crystal::Iconv::ERROR
+        if err == Crystal::Iconv::ERROR && Errno.value == Errno::EINVAL
           iconv.handle_invalid(pointerof(inbuf_ptr), pointerof(inbytesleft))
         end
         io.write(outbuf.to_slice[0, outbuf.size - outbytesleft])
@@ -1832,7 +1832,7 @@ class String
       outbuf_ptr = outbuf.to_unsafe
       outbytesleft = LibC::SizeT.new(outbuf.size)
       err = iconv.convert(Pointer(UInt8*).null, Pointer(LibC::SizeT).null, pointerof(outbuf_ptr), pointerof(outbytesleft))
-      if err == Crystal::Iconv::ERROR
+      if err == Crystal::Iconv::ERROR && Errno.value == Errno::EINVAL
         iconv.handle_invalid(pointerof(inbuf_ptr), pointerof(inbytesleft))
       end
       io.write(outbuf.to_slice[0, outbuf.size - outbytesleft])