diff --git a/Parsedown.php b/Parsedown.php
index 15c5c9c..fb6aa3a 100755
--- a/Parsedown.php
+++ b/Parsedown.php
@@ -1312,6 +1312,11 @@ class Parsedown
 
         $Span = $this->identifyLink($Excerpt);
 
+        if ($Span === null)
+        {
+            return;
+        }
+
         $Span['extent'] ++;
 
         $Span['element'] = array(
diff --git a/test/data/image_reference.html b/test/data/image_reference.html
index 6e45cba..67fbd2c 100644
--- a/test/data/image_reference.html
+++ b/test/data/image_reference.html
@@ -1 +1,2 @@
-<p><img src="/md.png" alt="Markdown Logo" /></p>
\ No newline at end of file
+<p><img src="/md.png" alt="Markdown Logo" /></p>
+<p>![missing reference]</p>
\ No newline at end of file
diff --git a/test/data/image_reference.md b/test/data/image_reference.md
index dcb1414..1e11d94 100644
--- a/test/data/image_reference.md
+++ b/test/data/image_reference.md
@@ -1,3 +1,5 @@
 ![Markdown Logo][image]
 
 [image]: /md.png
+
+![missing reference]
\ No newline at end of file