diff --git a/niworkflows/interfaces/utils.py b/niworkflows/interfaces/utils.py
index <HASH>..<HASH> 100644
--- a/niworkflows/interfaces/utils.py
+++ b/niworkflows/interfaces/utils.py
@@ -274,7 +274,8 @@ class SanitizeImageOutputSpec(TraitedSpec):
 class SanitizeImage(SimpleInterface):
     """
     Check the correctness of x-form headers (matrix and code) and fixes
-    problematic combinations of values.
+    problematic combinations of values. Removes any extension form the header
+    if present.
     This interface implements the `following logic
     <https://github.com/poldracklab/fmriprep/issues/873#issuecomment-349394544>`_:
     +-------------------+------------------+------------------+------------------\
@@ -392,6 +393,10 @@ class SanitizeImage(SimpleInterface):
                                  img.header)
             save_file = True
 
+        if len(img.header.extensions) != 0:
+            img.header.extensions.clear()
+            save_file = True
+
         # Store new file
         if save_file:
             out_fname = fname_presuffix(self.inputs.in_file, suffix='_valid',
remove extensions from the nifti header