diff --git a/lib/mudbrick.ex b/lib/mudbrick.ex
index 25f1480..eefc349 100644
--- a/lib/mudbrick.ex
+++ b/lib/mudbrick.ex
@@ -480,12 +480,13 @@ defmodule Mudbrick do
                 "Auto scaling works with width or height, but not both."
 
         {w, :auto} ->
-          ratio = w / image.width
-          {w, image.height * ratio}
+          scaled_height(w, image)
 
         {:auto, h} ->
-          ratio = h / image.height
-          {image.width * ratio, h}
+          scaled_width(h, image)
+
+        nil ->
+          scaled_height(100, image)
 
         otherwise ->
           otherwise
@@ -494,6 +495,16 @@ defmodule Mudbrick do
     Keyword.put(image_opts, :scale, scale)
   end
 
+  defp scaled_height(w, image) do
+    ratio = w / image.width
+    {w, image.height * ratio}
+  end
+
+  defp scaled_width(h, image) do
+    ratio = h / image.height
+    {image.width * ratio, h}
+  end
+
   defp fetch_font(doc, opts) do
     default_font =
       case Map.values(Document.root_page_tree(doc).value.fonts) do
diff --git a/lib/mudbrick/parser.ex b/lib/mudbrick/parser.ex
index 702d6a3..4e7b4f2 100644
--- a/lib/mudbrick/parser.ex
+++ b/lib/mudbrick/parser.ex
@@ -390,10 +390,13 @@ defmodule Mudbrick.Parser do
     if data == "" do
       []
     else
-      %Mudbrick.ContentStream{operations: operations} =
-        to_mudbrick(data, :content_blocks)
+      case to_mudbrick(data, :content_blocks) do
+        %Mudbrick.ContentStream{operations: operations} ->
+          operations
 
-      operations
+        _ ->
+          raise Error, "Can't parse content blocks: #{data}"
+      end
     end
   end
 
diff --git a/test/mudbrick/parser/roundtrip_test.exs b/test/mudbrick/parser/roundtrip_test.exs
index 50093b1..d880919 100644
--- a/test/mudbrick/parser/roundtrip_test.exs
+++ b/test/mudbrick/parser/roundtrip_test.exs
@@ -21,18 +21,17 @@ defmodule Mudbrick.ParseRoundtripTest do
           if(Enum.empty?(images_options), do: [], else: Stream.cycle(images_options)),
           if(Enum.empty?(images), do: [], else: Stream.cycle(Map.keys(images)))
         ])
-        |> Enum.reduce(doc, fn {page_options, _image_options, _image_identifier}, context ->
+        |> Enum.reduce(doc, fn {page_options, image_options, image_identifier}, context ->
           context
           |> page(page_options)
-
-          # |> then(fn page_context ->
-          #   if Enum.empty?(image_options) or Enum.empty?(document_options[:images]) do
-          #     page_context
-          #   else
-          #     page_context
-          #     |> image(image_identifier, image_options)
-          #   end
-          # end)
+          |> then(fn page_context ->
+            if Enum.empty?(image_options) or Enum.empty?(document_options[:images]) do
+              page_context
+            else
+              page_context
+              |> image(image_identifier, image_options)
+            end
+          end)
         end)
         |> render()
 
diff --git a/test/test_helper.exs b/test/test_helper.exs
index 490c9b4..a6348fe 100644
--- a/test/test_helper.exs
+++ b/test/test_helper.exs
@@ -184,7 +184,7 @@ defmodule Mudbrick.TestHelper do
   end
 
   def coords do
-    {float(max: 999), float(max: 999)}
+    {float_non_exponential(), float_non_exponential()}
   end
 
   def non_negative_coords do
@@ -193,11 +193,15 @@ defmodule Mudbrick.TestHelper do
 
   def scale do
     bind(one_of([:x_auto, :y_auto, :neither]), fn
-      :x_auto -> {:auto, float()}
-      :y_auto -> {float(), :auto}
-      :neither -> {float(), float()}
+      :x_auto -> {:auto, float_non_exponential()}
+      :y_auto -> {float_non_exponential(), :auto}
+      :neither -> coords()
     end)
   end
+
+  defp float_non_exponential do
+    float(min: -999, max: 999)
+  end
 end
 
 ExUnit.start()