diff --git a/biojava-structure/src/main/java/org/biojava/nbio/structure/symmetry/utils/SymmetryTools.java b/biojava-structure/src/main/java/org/biojava/nbio/structure/symmetry/utils/SymmetryTools.java
index <HASH>..<HASH> 100644
--- a/biojava-structure/src/main/java/org/biojava/nbio/structure/symmetry/utils/SymmetryTools.java
+++ b/biojava-structure/src/main/java/org/biojava/nbio/structure/symmetry/utils/SymmetryTools.java
@@ -518,6 +518,7 @@ public class SymmetryTools {
 		for (int i = 0; i < order; i++) {
 
 			Structure s = new StructureImpl();
+			s.addModel(new ArrayList<Chain>(1));
 			s.setStructureIdentifier(repeatsId.get(i));
 
 			Block align = symmetry.getMultipleAlignment().getBlock(0);
Quick fix of #<I>, following 'users should create models'

We might still need to do this elsewhere, or may want to
fix it more thoroughly elsewhere