diff -NurpP --minimal mysql-5.0.18/sql/ha_federated.cc mysql-5.0.18-fixed/sql/ha_federated.cc
--- mysql-5.0.18/sql/ha_federated.cc	2005-12-21 20:39:39.000000000 +0100
+++ mysql-5.0.18-fixed/sql/ha_federated.cc	2006-01-14 21:13:45.000000000 +0100
@@ -1846,11 +1846,11 @@ int ha_federated::update_row(const byte 
       /* otherwise = */
       (*field)->val_str(&new_field_value);
       (*field)->quote_data(&new_field_value);
-
-      if (!field_in_record_is_null(table, *field, (char*) old_data))
-        where_string.append(FEDERATED_EQ);
     }
 
+    update_string.append(new_field_value);
+    new_field_value.length(0);
+
     if (field_in_record_is_null(table, *field, (char*) old_data))
       where_string.append(FEDERATED_ISNULL);
     else
@@ -1858,12 +1858,10 @@ int ha_federated::update_row(const byte 
       (*field)->val_str(&old_field_value,
                         (char*) (old_data + (*field)->offset()));
       (*field)->quote_data(&old_field_value);
+      where_string.append(FEDERATED_EQ);
       where_string.append(old_field_value);
     }
 
-    update_string.append(new_field_value);
-    new_field_value.length(0);
-
     /*
       Only append conjunctions if we have another field in which
       to iterate