diff --git a/mrdna/readers/cadnano_segments.py b/mrdna/readers/cadnano_segments.py
index 0c402e60ff8a00ee3290edc164272e2e6d64c105..bc69c14c5da12282b7e66d93259c3d46721a59fe 100644
--- a/mrdna/readers/cadnano_segments.py
+++ b/mrdna/readers/cadnano_segments.py
@@ -472,12 +472,12 @@ class cadnano_part(SegmentModel):
 
     def _add_prime_ends(self):
         for h,fwd,z in self._5prime_list:
-            seg, nt = self._get_segment_nucleotide(h,z)
+            seg, nt = self._get_segment_nucleotide(h,z, fwd)
             # print("adding 5prime",seg.name,nt,fwd)
             seg.add_5prime(nt,fwd)
 
         for h,fwd,z in self._3prime_list:
-            seg, nt = self._get_segment_nucleotide(h,z)
+            seg, nt = self._get_segment_nucleotide(h,z, not fwd)
             # print("adding 3prime",seg.name,nt,fwd)
             seg.add_3prime(nt,fwd)