diff --git a/lib/heroicons.ex b/lib/heroicons.ex
index 0ab05b5..2707f4d 100644
--- a/lib/heroicons.ex
+++ b/lib/heroicons.ex
@@ -13,6 +13,8 @@ defmodule Heroicons do
     end
 
     icon_dir = Module.get_attribute(module, :icon_dir)
+    default_attrs =  Module.get_attribute(module, :default_attrs)
+
 
     icon_paths =
       Path.absname(icon_dir, :code.priv_dir(:heroicons))
@@ -20,12 +22,12 @@ defmodule Heroicons do
       |> Path.wildcard()
 
     for path <- icon_paths do
-      generate_function(path)
+      generate_function(path, default_attrs)
     end
   end
 
   @doc false
-  def generate_function(path) do
+  def generate_function(path, default_attrs) do
     name =
       Path.basename(path, ".svg")
       |> String.replace("-", "_")
@@ -33,8 +35,7 @@ defmodule Heroicons do
 
     icon = File.read!(path)
     {i, _} = :binary.match(icon, ">")
-
-    {head, tail} = String.split_at(icon, i)
+    {_, body} = String.split_at(icon, i)
 
     doc = """
     ![](assets/#{Path.relative_to(path, :code.priv_dir(:heroicons))}) {: width=24px}
@@ -48,16 +49,17 @@ defmodule Heroicons do
       @doc unquote(doc)
       @spec unquote(name)(keyword(binary)) :: binary
       def unquote(name)(opts \\ []) do
+        opts = Keyword.merge(unquote(default_attrs), opts)
         attrs =
           for {k, v} <- opts do
             safe_k =
               k |> Atom.to_string() |> String.replace("_", "-") |> Phoenix.HTML.Safe.to_iodata()
             safe_v = v |> Phoenix.HTML.Safe.to_iodata()
 
-            {:safe, [safe_k, ?=, ?", safe_v, ?"]}
+            {:safe, [?\s, safe_k, ?=, ?", safe_v, ?"]}
           end
 
-        {:safe, [unquote(head), Phoenix.HTML.Safe.to_iodata(attrs), unquote(tail)]}
+        {:safe, ["<svg", Phoenix.HTML.Safe.to_iodata(attrs), unquote(body)]}
       end
     end
   end
diff --git a/lib/heroicons/outline.ex b/lib/heroicons/outline.ex
index f9868c2..66074df 100644
--- a/lib/heroicons/outline.ex
+++ b/lib/heroicons/outline.ex
@@ -5,5 +5,6 @@ defmodule Heroicons.Outline do
   For primary navigation and marketing sections, designed to be rendered at 24x24.
   """
   @icon_dir "outline/"
+  @default_attrs [xmlns: "http://www.w3.org/2000/svg", fill: "none", viewBox: "0 0 24 24", stroke: "currentColor"]
   @before_compile Heroicons
 end
diff --git a/lib/heroicons/solid.ex b/lib/heroicons/solid.ex
index 74d7ece..3da2af9 100644
--- a/lib/heroicons/solid.ex
+++ b/lib/heroicons/solid.ex
@@ -6,5 +6,6 @@ defmodule Heroicons.Solid do
   """
 
   @icon_dir "solid/"
+  @default_attrs [xmlns: "http://www.w3.org/2000/svg", viewBox: "0 0 20 20", fill: "currentColor"]
   @before_compile Heroicons
 end
diff --git a/test/heroicons_test.exs b/test/heroicons_test.exs
index bd2ec6b..99298e7 100644
--- a/test/heroicons_test.exs
+++ b/test/heroicons_test.exs
@@ -26,6 +26,14 @@ defmodule HeroiconsTest do
     assert Heroicons.Outline.academic_cap(multiword_key: "foo")
            |> Phoenix.HTML.safe_to_string() =~
              ~s(multiword-key="foo")
+
+    assert Heroicons.Outline.academic_cap(viewBox: "0 0 12 12")
+           |> Phoenix.HTML.safe_to_string() =~
+             ~s(viewBox=\"0 0 12 12\")
+
+    refute Heroicons.Outline.academic_cap(viewBox: "0 0 12 12")
+           |> Phoenix.HTML.safe_to_string() =~
+             ~s(viewBox=\"0 0 24 24\")
   end
 
   test "generated docs" do