diff --git a/CHANGES.md b/CHANGES.md
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,3 +1,19 @@
+Version 0.4.7.0:  (2014-11-19)
+
+  * `foldt` tweaked to be made slightly lazier,  thus also affecting
+    `mergeAll`,  `mergeAllBy`, `unionAll`, and `unionAllBy`.  Thanks
+    goes to Will Ness for providing the following example that
+    previously entered into an infinite non-productive loop:
+
+~~~
+    let ps=3:minus[5,7..] (unionAll [[p*p,p*(p+2)..]|p<-ps]) in take 100 (2:ps)
+~~~
+
+    Note that the _de facto_ semantics of `foldt` has been modified
+    slightly:  instead of computing the sum of a list,  it computes
+    the sum of a list plus zero.   Of course,  if zero is a true
+    identity of plus,  then this change is of no semantic consequence.
+
 Version 0.4.6.1:  (2014-04-19)
 
   * Added strictness annotations inside of sortOn and nubSortOn
diff --git a/Data/List/Ordered.hs b/Data/List/Ordered.hs
--- a/Data/List/Ordered.hs
+++ b/Data/List/Ordered.hs
@@ -470,12 +470,9 @@
 -- is lazier than 'foldt''.   'foldt' is used in the implementation of
 -- 'mergeAll' and 'unionAll'.
 foldt :: (a -> a -> a) -> a -> [a] -> a
-foldt plus zero xs
-  = case xs of
-      []    -> zero
-      (_:_) -> loop xs
+foldt plus zero = loop
   where
-    loop [x]    = x
+    loop []     = zero
     loop (x:xs) = x `plus` loop (pairs xs)
 
     pairs (x:y:zs) = plus x y : pairs zs
diff --git a/data-ordlist.cabal b/data-ordlist.cabal
--- a/data-ordlist.cabal
+++ b/data-ordlist.cabal
@@ -1,5 +1,5 @@
 Name:                data-ordlist
-Version:             0.4.6.1
+Version:             0.4.7.0
 Description:
    This module provides set and multiset operations on ordered lists.
 License:             BSD3
@@ -23,4 +23,4 @@
 source-repository this
   type:      darcs
   location:  http://hub.darcs.net/lpsmith/data-ordlist
-  tag:       0.4.6.1
+  tag:       0.4.7.0