diff --git a/exact_cover/wrapper.py b/exact_cover/wrapper.py
index bf9d5d7..463c250 100644
--- a/exact_cover/wrapper.py
+++ b/exact_cover/wrapper.py
@@ -37,7 +37,7 @@ def truncate(row):
         if all(x == 0 for x in row):
             return [0]
         else:
-            if row[-1] == 0:
+            if row[-1] == -1:
                 return truncate(row[:-1])
             else:
                 return row
diff --git a/src/dlx.c b/src/dlx.c
index bdb800e..9eae403 100644
--- a/src/dlx.c
+++ b/src/dlx.c
@@ -117,7 +117,7 @@ int enumerate(list sparse_matrix, int k, int max, int *solution, int *solutions,
             solutions[i] = solution[i];
 	}
 	for (int i=k; i < solution_size; i++) {
-	    solutions[i] = 0;
+	    solutions[i] = -1;
 	}
 	return 1;
     }