diff --git a/pinry/pins/forms.py b/pinry/pins/forms.py
index 21f929a..c3175fd 100644
--- a/pinry/pins/forms.py
+++ b/pinry/pins/forms.py
@@ -8,11 +8,15 @@ class PinForm(forms.ModelForm):
 
     def clean_url(self):
         data = self.cleaned_data['url']
-        image_file_types = ['png', 'gif', 'jpeg', 'jpg']
-        file_type = data.split('.')[-1]
-        if file_type.lower() not in image_file_types:
-            raise forms.ValidationError("Requested URL is not an image file. Only images are currently supported.")
-        return data
+        try:
+            Pin.objects.get(url=data)
+            raise forms.ValidationError("URL has already been pinned!")
+        except Pin.DoesNotExist:
+            image_file_types = ['png', 'gif', 'jpeg', 'jpg']
+            file_type = data.split('.')[-1]
+            if file_type.lower() not in image_file_types:
+                raise forms.ValidationError("Requested URL is not an image file. Only images are currently supported.")
+            return data
 
     class Meta:
         model = Pin