diff --git a/src/main/java/no/birkett/kiwi/Solver.java b/src/main/java/no/birkett/kiwi/Solver.java
index c150020..ccb6522 100644
--- a/src/main/java/no/birkett/kiwi/Solver.java
+++ b/src/main/java/no/birkett/kiwi/Solver.java
@@ -219,7 +219,7 @@ public class Solver {
             if (row.coefficientFor(tag.marker) < 0.0)
                 return tag.marker;
         }
-        if (tag.other.getType() == Symbol.Type.SLACK || tag.other.getType() == Symbol.Type.ERROR) {
+        if (tag.other != null && (tag.other.getType() == Symbol.Type.SLACK || tag.other.getType() == Symbol.Type.ERROR)) {
             if (row.coefficientFor(tag.other) < 0.0)
                 return tag.other;
         }