diff --git a/compact/materials.xml b/compact/materials.xml
index 6f7d2641b29cc0122a45df8bd09fa17dda42bb6e..10a36b7e98094423f64089fd1242755dd4d7adab 100644
--- a/compact/materials.xml
+++ b/compact/materials.xml
@@ -185,12 +185,12 @@
     <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>
 
   <material name="Ar10CO2">
     <D type="density" value="1.802" unit="mg / cm3"/>