diff --git a/DiscImageChef.Filesystems/extFS.cs b/DiscImageChef.Filesystems/extFS.cs
index e36969c52..f2ca2969d 100644
--- a/DiscImageChef.Filesystems/extFS.cs
+++ b/DiscImageChef.Filesystems/extFS.cs
@@ -61,6 +61,9 @@ namespace DiscImageChef.Filesystems
 
         public override bool Identify(ImagePlugins.ImagePlugin imagePlugin, Partition partition)
         {
+            if(imagePlugin.GetSectorSize() < 512)
+                return false;
+            
             ulong sbSector = sbPos / imagePlugin.GetSectorSize();
             uint sbOff = sbPos % imagePlugin.GetSectorSize();
 
@@ -82,6 +85,9 @@ namespace DiscImageChef.Filesystems
 
             StringBuilder sb = new StringBuilder();
 
+            if(imagePlugin.GetSectorSize() < 512)
+                return;
+
             ulong sbSector = sbPos / imagePlugin.GetSectorSize();
             uint sbOff = sbPos % imagePlugin.GetSectorSize();