diff --git a/main/src/com/google/refine/sorting/BooleanCriterion.java b/main/src/com/google/refine/sorting/BooleanCriterion.java
index fb101c9d8..1f56c98de 100644
--- a/main/src/com/google/refine/sorting/BooleanCriterion.java
+++ b/main/src/com/google/refine/sorting/BooleanCriterion.java
@@ -53,7 +53,7 @@ public class BooleanCriterion extends Criterion {
                         return s_error;
                     }
                 }
-                return value;
+                return null;
             }
 
             @Override
diff --git a/main/src/com/google/refine/sorting/NumberCriterion.java b/main/src/com/google/refine/sorting/NumberCriterion.java
index b9af38b15..287618c35 100644
--- a/main/src/com/google/refine/sorting/NumberCriterion.java
+++ b/main/src/com/google/refine/sorting/NumberCriterion.java
@@ -66,7 +66,7 @@ public class NumberCriterion extends Criterion {
                     }
                     return s_error;
                 }
-                return value;
+                return null;
             }
 
             @Override