diff --git a/nii2dcm/nii.py b/nii2dcm/nii.py
index 7aa11ca..4ab899c 100644
--- a/nii2dcm/nii.py
+++ b/nii2dcm/nii.py
@@ -31,8 +31,13 @@ def fnT1N(A, N):
             nX, nY, nZ, nF = nib_nii.header['dim'][1], nib_nii.header['dim'][2], nib_nii.header['dim'][3], 1
             dimX, dimY, dimZ = nib_nii.header['pixdim'][1], nib_nii.header['pixdim'][2], nib_nii.header['pixdim'][3]
 
-        elif nib_nii.header['dim'][4] > 1:
-            print("Warning: Nifti is not 3-dimensional.")
+        elif nib_nii.header['dim'][0] == 3 and all([x > 1 for x in nib_nii.header['dim'][1:4]]):
+            nX, nY, nZ, nF = (nib_nii.header['dim'][1:4].tolist() + [1])
+            dimX, dimY, dimZ = nib_nii.header['pixdim'][1:4].tolist()
+
+        else:
+            print("Error: NIfTI is not 3-dimensional.")
+            exit(1)
 
         # Instances & Slice Spacing
         nInstances = nZ*nF