diff --git a/differential-dataflow/src/trace/implementations/ord_neu.rs b/differential-dataflow/src/trace/implementations/ord_neu.rs
index 0356ddf41..4ac2acf30 100644
--- a/differential-dataflow/src/trace/implementations/ord_neu.rs
+++ b/differential-dataflow/src/trace/implementations/ord_neu.rs
@@ -270,14 +270,14 @@ pub mod val_batch {
         fn work(&mut self, source1: &OrdValBatch<L>, source2: &OrdValBatch<L>, fuel: &mut isize) {
 
             // An (incomplete) indication of the amount of work we've done so far.
-            let starting_updates = self.result.times.len();
+            let starting_updates = self.result.times.len() + self.singletons;
             let mut effort = 0isize;
 
             // While both mergees are still active, perform single-key merges.
             while self.key_cursor1 < source1.storage.keys.len() && self.key_cursor2 < source2.storage.keys.len() && effort < *fuel {
                 self.merge_key(&source1.storage, &source2.storage);
                 // An (incomplete) accounting of the work we've done.
-                effort = (self.result.times.len() - starting_updates) as isize;
+                effort = (self.result.times.len() + self.singletons - starting_updates) as isize;
             }
 
             // Merging is complete, and only copying remains. 
@@ -285,12 +285,12 @@ pub mod val_batch {
             while self.key_cursor1 < source1.storage.keys.len() && effort < *fuel {
                 self.copy_key(&source1.storage, self.key_cursor1);
                 self.key_cursor1 += 1;
-                effort = (self.result.times.len() - starting_updates) as isize;
+                effort = (self.result.times.len() + self.singletons - starting_updates) as isize;
             }
             while self.key_cursor2 < source2.storage.keys.len() && effort < *fuel {
                 self.copy_key(&source2.storage, self.key_cursor2);
                 self.key_cursor2 += 1;
-                effort = (self.result.times.len() - starting_updates) as isize;
+                effort = (self.result.times.len() + self.singletons - starting_updates) as isize;
             }
 
             *fuel -= effort;
@@ -864,14 +864,14 @@ pub mod key_batch {
         fn work(&mut self, source1: &OrdKeyBatch<L>, source2: &OrdKeyBatch<L>, fuel: &mut isize) {
 
             // An (incomplete) indication of the amount of work we've done so far.
-            let starting_updates = self.result.times.len();
+            let starting_updates = self.result.times.len() + self.singletons;
             let mut effort = 0isize;
 
             // While both mergees are still active, perform single-key merges.
             while self.key_cursor1 < source1.storage.keys.len() && self.key_cursor2 < source2.storage.keys.len() && effort < *fuel {
                 self.merge_key(&source1.storage, &source2.storage);
                 // An (incomplete) accounting of the work we've done.
-                effort = (self.result.times.len() - starting_updates) as isize;
+                effort = (self.result.times.len() + self.singletons - starting_updates) as isize;
             }
 
             // Merging is complete, and only copying remains.
@@ -879,12 +879,12 @@ pub mod key_batch {
             while self.key_cursor1 < source1.storage.keys.len() && effort < *fuel {
                 self.copy_key(&source1.storage, self.key_cursor1);
                 self.key_cursor1 += 1;
-                effort = (self.result.times.len() - starting_updates) as isize;
+                effort = (self.result.times.len() + self.singletons - starting_updates) as isize;
             }
             while self.key_cursor2 < source2.storage.keys.len() && effort < *fuel {
                 self.copy_key(&source2.storage, self.key_cursor2);
                 self.key_cursor2 += 1;
-                effort = (self.result.times.len() - starting_updates) as isize;
+                effort = (self.result.times.len() + self.singletons - starting_updates) as isize;
             }
 
             *fuel -= effort;