diff --git a/materials.xml b/materials.xml
index b2b69be95c253d2b633b38ff98fc10199b8e99d2..cd1ec3eaa0e2321ba08925b05fe9dc5cf2ea7b06 100644
--- a/materials.xml
+++ b/materials.xml
@@ -184,11 +184,11 @@
     <composite n="1" ref="W"/>
     <composite n="4" ref="O"/>
   </material>
-	<material name="Ar10CO2">
-		<D type="density" value= "1.802e-3" unit="g / cm3"/>
-		<composite n="10" ref="Ar"/>
-		<composite n="1"  ref ="C"/>
-		<composite n="2"  ref="O"/>
-	</material>
+  <material name="Ar10CO2">
+    <D type="density" value= "1.802e-3" unit="g / cm3"/>
+    <composite n="10" ref="Ar"/>
+    <composite n="1"  ref ="C"/>
+    <composite n="2"  ref="O"/>
+  </material>
 
 </materials>