diff --git a/lib/phaxio/resources/webhook.rb b/lib/phaxio/resources/webhook.rb
index a05c0ae..8762811 100644
--- a/lib/phaxio/resources/webhook.rb
+++ b/lib/phaxio/resources/webhook.rb
@@ -57,7 +57,9 @@ def files_to_array(files)
         end
 
         def generate_file_string(file)
-          file[:name] + DIGEST.hexdigest(file[:tempfile].read)
+          file_string = file[:name] + DIGEST.hexdigest(file[:tempfile].read)
+          file[:tempfile].rewind
+          file_string
         end
       end
     end
diff --git a/spec/resources/webhook_spec.rb b/spec/resources/webhook_spec.rb
index 80a71a2..5c18637 100644
--- a/spec/resources/webhook_spec.rb
+++ b/spec/resources/webhook_spec.rb
@@ -30,5 +30,39 @@
         expect(result).to eq(false)
       end
     end
+
+    context 'with files' do
+      let(:signature) { '1d2426c242a8c5de7eb1d9b662b7fda1d0b6edab' }
+      let(:params) { { test: true } }
+
+      let(:file1) do
+        tempfile = Tempfile.new
+        tempfile.write("foo")
+        tempfile
+      end
+
+      let(:file2) do
+        tempfile = Tempfile.new
+        tempfile.write("bar")
+        tempfile
+      end
+
+      let(:files) do
+        [
+          { name: 'file', tempfile: file1 },
+          { name: 'file', tempfile: file2  }
+        ]
+      end
+
+      it 'returns true' do
+        result = action
+        expect(result).to eq(true)
+      end
+
+      it 'rewinds the files' do
+        action
+        expect(files.all? { |f| f[:tempfile].pos.zero? }).to eq(true)
+      end
+    end
   end
 end