diff --git a/CHANGELOG.md b/CHANGELOG.md
index 28fcbf7..78530ae 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changelog
 
+## Unreleased
+
+- raise on invalid UInt8 and Int8 when encoding RowBinary https://github.com/plausible/ch/pull/180
+
 ## 0.2.6 (2024-05-30)
 
 - fix query encoding for datetimes where the microseconds value starts with zeroes `~U[****-**-** **:**:**.0*****]` https://github.com/plausible/ch/pull/175
diff --git a/lib/ch/row_binary.ex b/lib/ch/row_binary.ex
index 22d477b..d2081b7 100644
--- a/lib/ch/row_binary.ex
+++ b/lib/ch/row_binary.ex
@@ -195,13 +195,23 @@ defmodule Ch.RowBinary do
 
   def encode({:fixed_string, size}, nil), do: <<0::size(size * 8)>>
 
-  def encode(:u8, u) when is_integer(u), do: u
+  # UInt8 — [0 : 255]
+  def encode(:u8, u) when is_integer(u) and u >= 0 and u <= 255, do: u
   def encode(:u8, nil), do: 0
 
-  def encode(:i8, i) when is_integer(i) and i >= 0, do: i
-  def encode(:i8, i) when is_integer(i), do: <<i::signed>>
+  def encode(:u8, term) do
+    raise ArgumentError, "invalid UInt8: #{inspect(term)}"
+  end
+
+  # Int8 — [-128 : 127]
+  def encode(:i8, i) when is_integer(i) and i >= 0 and i <= 127, do: i
+  def encode(:i8, i) when is_integer(i) and i < 0 and i >= -128, do: <<i::signed>>
   def encode(:i8, nil), do: 0
 
+  def encode(:i8, term) do
+    raise ArgumentError, "invalid Int8: #{inspect(term)}"
+  end
+
   for size <- [16, 32, 64, 128, 256] do
     def encode(unquote(:"u#{size}"), u) when is_integer(u) do
       <<u::unquote(size)-little>>
diff --git a/test/ch/row_binary_test.exs b/test/ch/row_binary_test.exs
index 497a61d..908a182 100644
--- a/test/ch/row_binary_test.exs
+++ b/test/ch/row_binary_test.exs
@@ -305,4 +305,20 @@ defmodule Ch.RowBinaryTest do
       assert decode_rows(<<1, 2>>, [:u8, :u8]) == [[1, 2]]
     end
   end
+
+  # TODO maybe use stream_data?
+  describe "invalid arguments" do
+    # https://github.com/plausible/ch/issues/166
+    test "for UInt8" do
+      assert_raise ArgumentError, "invalid UInt8: 256", fn -> encode(:u8, 256) end
+      assert_raise ArgumentError, "invalid UInt8: -1", fn -> encode(:u8, -1) end
+      assert_raise ArgumentError, "invalid UInt8: \"a\"", fn -> encode(:u8, "a") end
+    end
+
+    test "for Int8" do
+      assert_raise ArgumentError, "invalid Int8: 128", fn -> encode(:i8, 128) end
+      assert_raise ArgumentError, "invalid Int8: -129", fn -> encode(:i8, -129) end
+      assert_raise ArgumentError, "invalid Int8: \"a\"", fn -> encode(:i8, "a") end
+    end
+  end
 end