diff --git a/lib/postgrex/extensions/array.ex b/lib/postgrex/extensions/array.ex
index b180b9aa..92d3a959 100644
--- a/lib/postgrex/extensions/array.ex
+++ b/lib/postgrex/extensions/array.ex
@@ -28,15 +28,15 @@ defmodule Postgrex.Extensions.Array do
 
   def decode(_) do
     quote location: :keep do
-      <<len::int32(), binary::binary-size(len)>>, [oid], [type], mod ->
+      <<len::int32(), binary::binary-size(len)>>, [oid], [type] ->
         <<ndims::int32(), _has_null::int32(), ^oid::uint32(), dims::size(ndims)-binary-unit(64),
           data::binary>> = binary
 
         # decode_list/2 defined by TypeModule
         type =
           case type do
-            {extension, sub_oids, sub_types} -> {extension, sub_oids, sub_types, mod}
-            extension -> {extension, mod}
+            {extension, sub_oids, sub_types} -> {extension, sub_oids, sub_types, var!(mod)}
+            extension -> {extension, var!(mod)}
           end
 
         flat = decode_list(data, type)
diff --git a/lib/postgrex/extensions/multirange.ex b/lib/postgrex/extensions/multirange.ex
index 52cdfd7b..11bb2c20 100644
--- a/lib/postgrex/extensions/multirange.ex
+++ b/lib/postgrex/extensions/multirange.ex
@@ -27,7 +27,7 @@ defmodule Postgrex.Extensions.Multirange do
 
   def decode(_) do
     quote location: :keep do
-      <<len::int32(), data::binary-size(len)>>, [_oid], [type], _ ->
+      <<len::int32(), data::binary-size(len)>>, [_oid], [type] ->
         <<_num_ranges::int32(), ranges::binary>> = data
 
         # decode_list/2 defined by TypeModule
diff --git a/lib/postgrex/extensions/range.ex b/lib/postgrex/extensions/range.ex
index 69b1b5ac..92c0278f 100644
--- a/lib/postgrex/extensions/range.ex
+++ b/lib/postgrex/extensions/range.ex
@@ -35,7 +35,7 @@ defmodule Postgrex.Extensions.Range do
 
   def decode(_) do
     quote location: :keep do
-      <<len::int32(), binary::binary-size(len)>>, [_oid], [type], _ ->
+      <<len::int32(), binary::binary-size(len)>>, [_oid], [type] ->
         <<flags, data::binary>> = binary
 
         # decode_list/2 defined by TypeModule
diff --git a/lib/postgrex/extensions/record.ex b/lib/postgrex/extensions/record.ex
index 26a8d614..f436c671 100644
--- a/lib/postgrex/extensions/record.ex
+++ b/lib/postgrex/extensions/record.ex
@@ -31,12 +31,12 @@ defmodule Postgrex.Extensions.Record do
 
   def decode(_) do
     quote location: :keep do
-      <<len::int32(), binary::binary-size(len)>>, nil, types, _ ->
+      <<len::int32(), binary::binary-size(len)>>, nil, types ->
         <<count::int32(), data::binary>> = binary
         # decode_tuple/3 defined by TypeModule
         decode_tuple(data, count, types)
 
-      <<len::int32(), binary::binary-size(len)>>, oids, types, _ ->
+      <<len::int32(), binary::binary-size(len)>>, oids, types ->
         <<_::int32(), data::binary>> = binary
         # decode_tuple/3 defined by TypeModule
         decode_tuple(data, oids, types)
diff --git a/lib/postgrex/extensions/timestamp.ex b/lib/postgrex/extensions/timestamp.ex
index 0bc6779c..27184109 100644
--- a/lib/postgrex/extensions/timestamp.ex
+++ b/lib/postgrex/extensions/timestamp.ex
@@ -28,8 +28,8 @@ defmodule Postgrex.Extensions.Timestamp do
 
   def decode(infinity?) do
     quote location: :keep do
-      <<8::int32(), microsecs::int64()>>, precision ->
-        unquote(__MODULE__).microsecond_to_elixir(microsecs, precision, unquote(infinity?))
+      <<8::int32(), microsecs::int64()>> ->
+        unquote(__MODULE__).microsecond_to_elixir(microsecs, var!(mod), unquote(infinity?))
     end
   end
 
diff --git a/lib/postgrex/type_module.ex b/lib/postgrex/type_module.ex
index 2c53ead6..41504e70 100644
--- a/lib/postgrex/type_module.ex
+++ b/lib/postgrex/type_module.ex
@@ -198,7 +198,7 @@ defmodule Postgrex.TypeModule do
   end
 
   defp encode_extension(extension, clause) do
-    case split_extension_encode(clause) do
+    case split_extension(clause) do
       {pattern, guard, body} ->
         encode_extension(extension, pattern, guard, body)
 
@@ -224,7 +224,7 @@ defmodule Postgrex.TypeModule do
   end
 
   defp encode_super(extension, clause) do
-    case split_super_encode(clause) do
+    case split_super(clause) do
       {pattern, sub_oids, sub_types, guard, body} ->
         encode_super(extension, pattern, sub_oids, sub_types, guard, body)
 
@@ -615,12 +615,11 @@ defmodule Postgrex.TypeModule do
   end
 
   defp decode_extension(extension, clause, dispatch, rest, acc, rem, full, rows) do
-    case split_extension_decode(clause) do
-      {pattern, mod, guard, body} ->
+    case split_extension(clause) do
+      {pattern, guard, body} ->
         decode_extension(
           extension,
           pattern,
-          mod,
           guard,
           body,
           dispatch,
@@ -631,15 +630,14 @@ defmodule Postgrex.TypeModule do
           rows
         )
 
-      {pattern, mod, body} ->
-        decode_extension(extension, pattern, mod, body, dispatch, rest, acc, rem, full, rows)
+      {pattern, body} ->
+        decode_extension(extension, pattern, body, dispatch, rest, acc, rem, full, rows)
     end
   end
 
   defp decode_extension(
          extension,
          pattern,
-         mod,
          guard,
          body,
          dispatch,
@@ -652,7 +650,7 @@ defmodule Postgrex.TypeModule do
     quote do
       defp unquote(extension)(
              <<unquote(pattern), unquote(rest)::binary>>,
-             unquote(mod),
+             var!(mod),
              types,
              acc,
              unquote(rem),
@@ -667,24 +665,24 @@ defmodule Postgrex.TypeModule do
         end
       end
 
-      defp unquote(extension)(<<unquote(pattern), rest::binary>>, mod = unquote(mod), acc)
+      defp unquote(extension)(<<unquote(pattern), rest::binary>>, var!(mod) = mod, acc)
            when unquote(guard) do
         unquote(extension)(rest, mod, [unquote(body) | acc])
       end
 
       defp unquote(extension)(
              <<unquote(pattern), rest::binary>>,
-             nil = unquote(mod),
+             var!(mod) = mod,
              acc,
              callback
            )
            when unquote(guard) do
-        unquote(extension)(rest, nil, [unquote(body) | acc], callback)
+        unquote(extension)(rest, mod, [unquote(body) | acc], callback)
       end
 
       defp unquote(extension)(
              <<unquote(pattern), rest::binary>>,
-             nil = unquote(mod),
+             var!(mod),
              oids,
              types,
              n,
@@ -696,11 +694,11 @@ defmodule Postgrex.TypeModule do
     end
   end
 
-  defp decode_extension(extension, pattern, mod, body, dispatch, rest, acc, rem, full, rows) do
+  defp decode_extension(extension, pattern, body, dispatch, rest, acc, rem, full, rows) do
     quote do
       defp unquote(extension)(
              <<unquote(pattern), unquote(rest)::binary>>,
-             unquote(mod),
+             var!(mod),
              types,
              acc,
              unquote(rem),
@@ -714,24 +712,24 @@ defmodule Postgrex.TypeModule do
         end
       end
 
-      defp unquote(extension)(<<unquote(pattern), rest::binary>>, mod = unquote(mod), acc) do
+      defp unquote(extension)(<<unquote(pattern), rest::binary>>, var!(mod), acc) do
         decoded = unquote(body)
-        unquote(extension)(rest, mod, [decoded | acc])
+        unquote(extension)(rest, var!(mod), [decoded | acc])
       end
 
       defp unquote(extension)(
              <<unquote(pattern), rest::binary>>,
-             nil = unquote(mod),
+             var!(mod),
              acc,
              callback
            ) do
         decoded = unquote(body)
-        unquote(extension)(rest, nil, [decoded | acc], callback)
+        unquote(extension)(rest, var!(mod), [decoded | acc], callback)
       end
 
       defp unquote(extension)(
              <<unquote(pattern), rest::binary>>,
-             nil = unquote(mod),
+             var!(mod),
              oids,
              types,
              n,
@@ -760,29 +758,29 @@ defmodule Postgrex.TypeModule do
         end
       end
 
-      defp unquote(extension)(<<-1::int32(), rest::binary>>, mod, acc) do
-        unquote(extension)(rest, mod, [@null | acc])
+      defp unquote(extension)(<<-1::int32(), rest::binary>>, var!(mod), acc) do
+        unquote(extension)(rest, var!(mod), [@null | acc])
       end
 
       defp unquote(extension)(<<>>, _, acc) do
         acc
       end
 
-      defp unquote(extension)(<<-1::int32(), rest::binary>>, nil, acc, callback) do
-        unquote(extension)(rest, nil, [@null | acc], callback)
+      defp unquote(extension)(<<-1::int32(), rest::binary>>, var!(mod), acc, callback) do
+        unquote(extension)(rest, var!(mod), [@null | acc], callback)
       end
 
       defp unquote(extension)(<<rest::binary-size(0)>>, _, acc, callback) do
         callback.(rest, acc)
       end
 
-      defp unquote(extension)(<<-1::int32(), rest::binary>>, nil, oids, types, n, acc) do
+      defp unquote(extension)(<<-1::int32(), rest::binary>>, _mod, oids, types, n, acc) do
         decode_tuple(rest, oids, types, n, acc)
       end
     end
   end
 
-  defp split_extension_encode({:->, _, [head, body]}) do
+  defp split_extension({:->, _, [head, body]}) do
     case head do
       [{:when, _, [pattern, guard]}] ->
         {pattern, guard, body}
@@ -792,31 +790,14 @@ defmodule Postgrex.TypeModule do
     end
   end
 
-  defp split_extension_decode({:->, _, [head, body]}) do
-    case head do
-      [{:when, _, [pattern, guard]}] ->
-        {pattern, quote(do: _), guard, body}
-
-      [pattern] ->
-        {pattern, quote(do: _), body}
-
-      [{:when, _, [pattern, modifier, guard]}] ->
-        {pattern, modifier, guard, body}
-
-      [pattern, modifier] ->
-        {pattern, modifier, body}
-    end
-  end
-
   defp decode_super(extension, clause, dispatch, rest, acc, rem, full, rows) do
-    case split_super_decode(clause) do
-      {pattern, oids, types, mod, guard, body} ->
+    case split_super(clause) do
+      {pattern, oids, types, guard, body} ->
         decode_super(
           extension,
           pattern,
           oids,
           types,
-          mod,
           guard,
           body,
           dispatch,
@@ -827,13 +808,12 @@ defmodule Postgrex.TypeModule do
           rows
         )
 
-      {pattern, oids, types, mod, body} ->
+      {pattern, oids, types, body} ->
         decode_super(
           extension,
           pattern,
           oids,
           types,
-          mod,
           body,
           dispatch,
           rest,
@@ -850,7 +830,6 @@ defmodule Postgrex.TypeModule do
          pattern,
          sub_oids,
          sub_types,
-         mod,
          guard,
          body,
          dispatch,
@@ -865,7 +844,7 @@ defmodule Postgrex.TypeModule do
              <<unquote(pattern), unquote(rest)::binary>>,
              unquote(sub_oids),
              unquote(sub_types),
-             unquote(mod),
+             var!(mod),
              types,
              acc,
              unquote(rem),
@@ -884,19 +863,19 @@ defmodule Postgrex.TypeModule do
              <<unquote(pattern), rest::binary>>,
              unquote(sub_oids),
              unquote(sub_types),
-             mod = unquote(mod),
+             var!(mod),
              acc
            )
            when unquote(guard) do
         acc = [unquote(body) | acc]
-        unquote(extension)(rest, unquote(sub_oids), unquote(sub_types), mod, acc)
+        unquote(extension)(rest, unquote(sub_oids), unquote(sub_types), var!(mod), acc)
       end
 
       defp unquote(extension)(
              <<unquote(pattern), rest::binary>>,
              unquote(sub_oids),
              unquote(sub_types),
-             nil = unquote(mod),
+             var!(mod),
              oids,
              types,
              n,
@@ -913,7 +892,6 @@ defmodule Postgrex.TypeModule do
          pattern,
          sub_oids,
          sub_types,
-         mod,
          body,
          dispatch,
          rest,
@@ -927,7 +905,7 @@ defmodule Postgrex.TypeModule do
              <<unquote(pattern), unquote(rest)::binary>>,
              unquote(sub_oids),
              unquote(sub_types),
-             unquote(mod),
+             var!(mod),
              types,
              acc,
              unquote(rem),
@@ -945,18 +923,18 @@ defmodule Postgrex.TypeModule do
              <<unquote(pattern), rest::binary>>,
              unquote(sub_oids),
              unquote(sub_types),
-             mod = unquote(mod),
+             var!(mod),
              acc
            ) do
         acc = [unquote(body) | acc]
-        unquote(extension)(rest, unquote(sub_oids), unquote(sub_types), mod, acc)
+        unquote(extension)(rest, unquote(sub_oids), unquote(sub_types), var!(mod), acc)
       end
 
       defp unquote(extension)(
              <<unquote(pattern), rest::binary>>,
              unquote(sub_oids),
              unquote(sub_types),
-             nil = unquote(mod),
+             var!(mod),
              oids,
              types,
              n,
@@ -988,8 +966,8 @@ defmodule Postgrex.TypeModule do
         end
       end
 
-      defp unquote(extension)(<<-1::int32(), rest::binary>>, sub_oids, sub_types, mod, acc) do
-        unquote(extension)(rest, sub_oids, sub_types, mod, [@null | acc])
+      defp unquote(extension)(<<-1::int32(), rest::binary>>, sub_oids, sub_types, var!(mod), acc) do
+        unquote(extension)(rest, sub_oids, sub_types, var!(mod), [@null | acc])
       end
 
       defp unquote(extension)(<<>>, _sub_oid, _sub_types, _mod, acc) do
@@ -1000,7 +978,7 @@ defmodule Postgrex.TypeModule do
              <<-1::int32(), rest::binary>>,
              _sub_oids,
              _sub_types,
-             nil,
+             _mod,
              oids,
              types,
              n,
@@ -1011,7 +989,7 @@ defmodule Postgrex.TypeModule do
     end
   end
 
-  defp split_super_encode({:->, _, [head, body]}) do
+  defp split_super({:->, _, [head, body]}) do
     case head do
       [{:when, _, [pattern, sub_oids, sub_types, guard]}] ->
         {pattern, sub_oids, sub_types, guard, body}
@@ -1021,16 +999,6 @@ defmodule Postgrex.TypeModule do
     end
   end
 
-  defp split_super_decode({:->, _, [head, body]}) do
-    case head do
-      [{:when, _, [pattern, sub_oids, sub_types, modifier, guard]}] ->
-        {pattern, sub_oids, sub_types, modifier, guard, body}
-
-      [pattern, sub_oids, sub_types, modifier] ->
-        {pattern, sub_oids, sub_types, modifier, body}
-    end
-  end
-
   defp configure(extensions, opts) do
     defaults = Postgrex.Utils.default_extensions(opts)
     Enum.map(extensions ++ defaults, &configure/1)