diff --git a/nipype/interfaces/spm/base.py b/nipype/interfaces/spm/base.py
index 42854f5f62..4eaa3b187b 100644
--- a/nipype/interfaces/spm/base.py
+++ b/nipype/interfaces/spm/base.py
@@ -324,7 +324,10 @@ def _generate_job(self, prefix='', contents=None):
             return jobstring
         if isinstance(contents, list):
             for i,value in enumerate(contents):
-                newprefix = "%s(%d)" % (prefix, i+1)
+                if prefix.endswith(")"):
+                    newprefix = "%s,%d)" % (prefix[:-1], i+1)
+                else:
+                    newprefix = "%s(%d)" % (prefix, i+1)
                 jobstring += self._generate_job(newprefix, value)
             return jobstring
         if isinstance(contents, dict):
diff --git a/nipype/interfaces/spm/preprocess.py b/nipype/interfaces/spm/preprocess.py
index 638df1a58f..5b73d9ad60 100644
--- a/nipype/interfaces/spm/preprocess.py
+++ b/nipype/interfaces/spm/preprocess.py
@@ -353,7 +353,7 @@ class NormalizeInputSpec(SPMCommandInputSpec):
                                             desc='the amount of the regularization for the nonlinear part of the normalization (opt)')
     write_preserve = traits.Bool(field='roptions.preserve',
                      desc='True/False warped images are modulated (opt,)')
-    write_bounding_box = traits.List(traits.Float(), field='roptions.bb', minlen=6, maxlen=6, desc='6-element list (opt)')
+    write_bounding_box = traits.List(traits.List(traits.Float(), minlen=3, maxlen=3), field='roptions.bb', minlen=2, maxlen=2, desc='3x2-element list of lists (opt)')
     write_voxel_sizes = traits.List(traits.Float(), field='roptions.vox', minlen=3, maxlen=3, desc='3-element list (opt)')
     write_interp = traits.Range(low=0, hign=7, field='roptions.interp',
                         desc='degree of b-spline used for interpolation')