diff --git a/ChangeLog b/ChangeLog
index e5c8e5aad..4aa624fa7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2011-11-04  Richard Frith-Macdonald <rfm@gnu.org>
+
+	* Source/NSDate.m:  ([-timeIntervalSinceDate:]) return NaN if other
+	date is nil (OSX compatibility).
+
 2011-11-02  Richard Frith-Macdonald <rfm@gnu.org>
 
 	* Source/NSNumber.m: Fix alignment error when encoding/decoding ...
diff --git a/Source/NSDate.m b/Source/NSDate.m
index 4d7769859..3f56ff573 100644
--- a/Source/NSDate.m
+++ b/Source/NSDate.m
@@ -1226,15 +1226,20 @@ otherTime(NSDate* other)
 /**
  * Returns the time interval between the receivers value and that of the
  * otherDate argument.  If otherDate is earlier than the receiver, the
- * returned value will be positive, if it is later it will be negative.
+ * returned value will be positive, if it is later it will be negative.<br />
+ * For current (2011) OSX compatibility, this method returns NaN if otherDate
+ * is nil ... do not write code depending on that behavior.
  */
 - (NSTimeInterval) timeIntervalSinceDate: (NSDate*)otherDate
 {
   if (otherDate == nil)
+    return nan("");
+/*
     {
       [NSException raise: NSInvalidArgumentException
 		  format: @"nil argument for timeIntervalSinceDate:"];
     }
+*/
   return otherTime(self) - otherTime(otherDate);
 }