diff --git a/src/SIL.Machine/Corpora/NParallelTextCorpus.cs b/src/SIL.Machine/Corpora/NParallelTextCorpus.cs
index d3df81da..b496e584 100644
--- a/src/SIL.Machine/Corpora/NParallelTextCorpus.cs
+++ b/src/SIL.Machine/Corpora/NParallelTextCorpus.cs
@@ -186,6 +186,8 @@ NParallelTextRow row in CreateMinRefRows(
                     }
                     foreach (int i in minRefIndexes)
                     {
+                        if (completed[i])
+                            continue;
                         sameRefRows[i].Add(enumerators[i].Current);
                         bool isCompleted = !enumerators[i].MoveNext();
                         completed[i] = isCompleted;
@@ -241,6 +243,8 @@ NParallelTextRow row in CreateRows(
 
                     for (int i = 0; i < rangeInfo.Rows.Count; i++)
                     {
+                        if (completed[i])
+                            continue;
                         sameRefRows[i].Add(currentRows[i]);
                         bool isCompleted = !enumerators[i].MoveNext();
                         completed[i] = isCompleted;