diff --git a/lib/new_relic/transaction/reporter.ex b/lib/new_relic/transaction/reporter.ex
index cceebaa2..d29b3840 100644
--- a/lib/new_relic/transaction/reporter.ex
+++ b/lib/new_relic/transaction/reporter.ex
@@ -18,7 +18,13 @@ defmodule NewRelic.Transaction.Reporter do
 
   def add_attributes(attrs) when is_list(attrs) do
     if tracking?(self()) do
-      AttrStore.add(__MODULE__, self(), NewRelic.Util.deep_flatten(attrs))
+      AttrStore.add(
+        __MODULE__,
+        self(),
+        attrs
+        |> NewRelic.Util.deep_flatten()
+        |> NewRelic.Util.coerce_attributes()
+      )
     end
   end
 
@@ -28,20 +34,19 @@ defmodule NewRelic.Transaction.Reporter do
     end
   end
 
-  def set_transaction_name(custom_name) do
+  def set_transaction_name(custom_name) when is_binary(custom_name) do
     if tracking?(self()) do
       AttrStore.add(__MODULE__, self(), custom_name: custom_name)
     end
   end
 
   # Internal Agent API
-  #
 
   def start() do
     Transaction.Monitor.add(self())
     AttrStore.track(__MODULE__, self())
 
-    add_attributes(
+    AttrStore.add(__MODULE__, self(),
       pid: inspect(self()),
       start_time: System.system_time(),
       start_time_mono: System.monotonic_time()
@@ -66,7 +71,7 @@ defmodule NewRelic.Transaction.Reporter do
   def fail(%{kind: kind, reason: reason, stack: stack} = error) do
     if tracking?(self()) do
       if NewRelic.Config.feature?(:error_collector) do
-        add_attributes(
+        AttrStore.add(__MODULE__, self(),
           error: true,
           transaction_error: {:error, error},
           error_kind: kind,
@@ -74,7 +79,7 @@ defmodule NewRelic.Transaction.Reporter do
           error_stack: inspect(stack)
         )
       else
-        add_attributes(error: true)
+        AttrStore.add(__MODULE__, self(), error: true)
       end
     end
   end
diff --git a/lib/new_relic/util.ex b/lib/new_relic/util.ex
index 4b693a36..ec246737 100644
--- a/lib/new_relic/util.ex
+++ b/lib/new_relic/util.ex
@@ -41,6 +41,10 @@ defmodule NewRelic.Util do
     |> Enum.concat([{"#{key}.length", length(list_value)}])
   end
 
+  def deep_flatten({key, %{__struct__: _} = value}) do
+    [{key, value}]
+  end
+
   def deep_flatten({key, map_value}) when is_map(map_value) do
     map_value
     |> Enum.slice(0..9)
@@ -52,6 +56,36 @@ defmodule NewRelic.Util do
     [{key, value}]
   end
 
+  def coerce_attributes(attrs) do
+    Enum.map(attrs, fn
+      {key, value} when is_number(value) when is_boolean(value) ->
+        {key, value}
+
+      {key, value} when is_bitstring(value) ->
+        case String.valid?(value) do
+          true -> {key, value}
+          false -> bad_value(key, value)
+        end
+
+      {key, value} when is_reference(value) when is_pid(value) when is_port(value) ->
+        {key, inspect(value)}
+
+      {key, value} when is_atom(value) ->
+        {key, to_string(value)}
+
+      {key, %struct{} = value} when struct in [Date, DateTime, Time, NaiveDateTime] ->
+        {key, struct.to_iso8601(value)}
+
+      {key, value} ->
+        bad_value(key, value)
+    end)
+  end
+
+  defp bad_value(key, value) do
+    NewRelic.log(:debug, "Bad attribute value: #{inspect(key)} => #{inspect(value)}")
+    {key, "[BAD_VALUE]"}
+  end
+
   def elixir_environment() do
     build_info = System.build_info()
 
diff --git a/test/transaction_test.exs b/test/transaction_test.exs
index 461fec92..7836fbc1 100644
--- a/test/transaction_test.exs
+++ b/test/transaction_test.exs
@@ -37,6 +37,31 @@ defmodule TransactionTest do
       send_resp(conn, 200, "incr")
     end
 
+    get "/funky_attrs" do
+      NewRelic.add_attributes(
+        # allowed:
+        one: 1,
+        half: 0.5,
+        string: "A string",
+        bool: true,
+        atom: :atom,
+        pid: self(),
+        ref: make_ref(),
+        port: :erlang.list_to_port('#Port<0.4>'),
+        date: Date.utc_today(),
+        date_time: DateTime.utc_now(),
+        naive_date_time: NaiveDateTime.utc_now(),
+        time: Time.utc_now(),
+        # not allowed:
+        binary: "fooo" |> :zlib.gzip(),
+        struct: %NewRelic.Metric{},
+        tuple: {:one, :two},
+        function: fn -> :fun! end
+      )
+
+      send_resp(conn, 200, "funky_attrs")
+    end
+
     get "/service" do
       NewRelic.set_transaction_name("/service")
       NewRelic.add_attributes(query: "query{}")
@@ -134,6 +159,42 @@ defmodule TransactionTest do
            end)
   end
 
+  @bad "[BAD_VALUE]"
+  test "Attribute coercion" do
+    TestHelper.restart_harvest_cycle(Collector.TransactionEvent.HarvestCycle)
+
+    TestHelper.request(TestPlugApp, conn(:get, "/funky_attrs"))
+
+    events = TestHelper.gather_harvest(Collector.TransactionEvent.Harvester)
+
+    [_, event] = Enum.find(events, fn [_, event] -> event[:name] == "/Plug/GET//funky_attrs" end)
+
+    # Basic values
+    assert event[:one] == 1
+    assert event[:half] == 0.5
+    assert event[:bool] == true
+    assert event[:string] == "A string"
+    assert event[:atom] == "atom"
+
+    # Fancy values
+    assert event[:pid] =~ "#PID"
+    assert event[:ref] =~ "#Reference"
+    assert event[:port] =~ "#Port"
+    assert {:ok, _, _} = DateTime.from_iso8601(event[:date_time])
+    assert {:ok, _} = NaiveDateTime.from_iso8601(event[:naive_date_time])
+    assert {:ok, _} = Date.from_iso8601(event[:date])
+    assert {:ok, _} = Time.from_iso8601(event[:time])
+
+    # Bad values
+    assert event[:binary] == @bad
+    assert event[:tuple] == @bad
+    assert event[:function] == @bad
+    assert event[:struct] == @bad
+
+    # Make sure it can serialize to JSON
+    Jason.encode!(events)
+  end
+
   test "Incrementing attribute counters" do
     TestHelper.restart_harvest_cycle(Collector.TransactionEvent.HarvestCycle)