diff --git a/dfvfs/analyzer/ext_analyzer_helper.py b/dfvfs/analyzer/ext_analyzer_helper.py
index 6f498e7b..2ffddda0 100644
--- a/dfvfs/analyzer/ext_analyzer_helper.py
+++ b/dfvfs/analyzer/ext_analyzer_helper.py
@@ -28,9 +28,17 @@ def GetFormatSpecification(self):
         self.type_indicator)
 
     # EXT file system signature.
-    format_specification.AddNewSignature(b'\x53\xef', offset=56)
+    format_specification.AddNewSignature(b'\x53\xef', offset=1080)
 
     return format_specification
 
+  def IsEnabled(self):
+    """Determines if the analyzer helper is enabled.
+
+    Returns:
+      bool: True if the analyzer helper is enabled.
+    """
+    return definitions.PREFERRED_EXT_BACK_END == self.TYPE_INDICATOR
+
 
 analyzer.Analyzer.RegisterHelper(EXTAnalyzerHelper())
diff --git a/dfvfs/analyzer/tsk_analyzer_helper.py b/dfvfs/analyzer/tsk_analyzer_helper.py
index 9dbdf1fb..b920c853 100644
--- a/dfvfs/analyzer/tsk_analyzer_helper.py
+++ b/dfvfs/analyzer/tsk_analyzer_helper.py
@@ -46,8 +46,9 @@ def GetFormatSpecification(self):
     # HFSX file system signature.
     format_specification.AddNewSignature(b'HX', offset=1024)
 
-    # Ext file system signature.
-    format_specification.AddNewSignature(b'\x53\xef', offset=1080)
+    if definitions.PREFERRED_EXT_BACK_END == self.TYPE_INDICATOR:
+      # Ext file system signature.
+      format_specification.AddNewSignature(b'\x53\xef', offset=1080)
 
     # ISO9660 file system signature.
     format_specification.AddNewSignature(b'CD001', offset=32769)