diff --git a/fsl/data/dicom.py b/fsl/data/dicom.py
index bf1bb5de4f5f35bdc970fe18ebbe8970d0d5b2ec..88d4f602347e4eec22f36bb9c9313bc2dcd0d307 100644
--- a/fsl/data/dicom.py
+++ b/fsl/data/dicom.py
@@ -206,6 +206,9 @@ def loadSeries(series):
             sp.call(cmd.split(), stdout=devnull, stderr=devnull)
 
         files  = glob.glob(op.join(td, '{}.nii'.format(snum)))
-        images = [nib.load(f, mmap=False) for f in files]
+        images = [nib.load(f) for f in files]
+
+        # Force-load images into memory
+        [i.get_data() for i in images]
 
         return [DicomImage(i, series, name=desc) for i in images]