diff --git a/graph/bolt/all_iterator.go b/graph/bolt/all_iterator.go
index 4cd017e..2c8d379 100644
--- a/graph/bolt/all_iterator.go
+++ b/graph/bolt/all_iterator.go
@@ -204,3 +204,5 @@ func (it *AllIterator) Stats() graph.IteratorStats {
 		Size:         s,
 	}
 }
+
+var _ graph.Nexter = &AllIterator{}
diff --git a/graph/bolt/iterator.go b/graph/bolt/iterator.go
index efb11d6..b7df4e9 100644
--- a/graph/bolt/iterator.go
+++ b/graph/bolt/iterator.go
@@ -316,3 +316,5 @@ func (it *Iterator) Stats() graph.IteratorStats {
 		Size:         s,
 	}
 }
+
+var _ graph.Nexter = &Iterator{}
diff --git a/graph/gaedatastore/iterator.go b/graph/gaedatastore/iterator.go
index ffdc8fe..8b8339d 100644
--- a/graph/gaedatastore/iterator.go
+++ b/graph/gaedatastore/iterator.go
@@ -323,3 +323,5 @@ func (it *Iterator) Stats() graph.IteratorStats {
 		Size:         size,
 	}
 }
+
+var _ graph.Nexter = &Iterator{}
diff --git a/graph/iterator/all_iterator.go b/graph/iterator/all_iterator.go
index d937ce4..31d4b8e 100644
--- a/graph/iterator/all_iterator.go
+++ b/graph/iterator/all_iterator.go
@@ -160,3 +160,5 @@ func (it *Int64) Stats() graph.IteratorStats {
 		Contains:     it.runstats.Contains,
 	}
 }
+
+var _ graph.Nexter = &Int64{}
diff --git a/graph/iterator/and_iterator.go b/graph/iterator/and_iterator.go
index 3764600..d8d45e5 100644
--- a/graph/iterator/and_iterator.go
+++ b/graph/iterator/and_iterator.go
@@ -265,3 +265,5 @@ func (it *And) Close() {
 
 // Register this as an "and" iterator.
 func (it *And) Type() graph.Type { return graph.And }
+
+var _ graph.Nexter = &And{}
diff --git a/graph/iterator/fixed_iterator.go b/graph/iterator/fixed_iterator.go
index 4a8afb9..fbfd310 100644
--- a/graph/iterator/fixed_iterator.go
+++ b/graph/iterator/fixed_iterator.go
@@ -186,3 +186,5 @@ func (it *Fixed) Stats() graph.IteratorStats {
 		Size:         int64(len(it.values)),
 	}
 }
+
+var _ graph.Nexter = &Fixed{}
diff --git a/graph/iterator/hasa_iterator.go b/graph/iterator/hasa_iterator.go
index 3788b40..adac2c8 100644
--- a/graph/iterator/hasa_iterator.go
+++ b/graph/iterator/hasa_iterator.go
@@ -252,3 +252,5 @@ func (it *HasA) Type() graph.Type { return graph.HasA }
 func (it *HasA) Size() (int64, bool) {
 	return it.Stats().Size, false
 }
+
+var _ graph.Nexter = &HasA{}
diff --git a/graph/iterator/iterator.go b/graph/iterator/iterator.go
index 954ddba..6495de0 100644
--- a/graph/iterator/iterator.go
+++ b/graph/iterator/iterator.go
@@ -116,3 +116,5 @@ func (it *Null) Close() {}
 func (it *Null) Stats() graph.IteratorStats {
 	return graph.IteratorStats{}
 }
+
+var _ graph.Nexter = &Null{}
diff --git a/graph/iterator/linksto_iterator.go b/graph/iterator/linksto_iterator.go
index 99a8df5..cc1cfa5 100644
--- a/graph/iterator/linksto_iterator.go
+++ b/graph/iterator/linksto_iterator.go
@@ -214,3 +214,5 @@ func (it *LinksTo) Stats() graph.IteratorStats {
 func (it *LinksTo) Size() (int64, bool) {
 	return it.Stats().Size, false
 }
+
+var _ graph.Nexter = &LinksTo{}
diff --git a/graph/iterator/materialize_iterator.go b/graph/iterator/materialize_iterator.go
index 00b2102..f771e89 100644
--- a/graph/iterator/materialize_iterator.go
+++ b/graph/iterator/materialize_iterator.go
@@ -293,3 +293,5 @@ func (it *Materialize) materializeSet() {
 	}
 	it.hasRun = true
 }
+
+var _ graph.Nexter = &Materialize{}
diff --git a/graph/iterator/not_iterator.go b/graph/iterator/not_iterator.go
index db394f8..3a3a4c4 100644
--- a/graph/iterator/not_iterator.go
+++ b/graph/iterator/not_iterator.go
@@ -161,3 +161,5 @@ func (it *Not) Describe() graph.Description {
 		Iterators: subIts,
 	}
 }
+
+var _ graph.Nexter = &Not{}
diff --git a/graph/iterator/or_iterator.go b/graph/iterator/or_iterator.go
index 6c58238..3c07b18 100644
--- a/graph/iterator/or_iterator.go
+++ b/graph/iterator/or_iterator.go
@@ -289,3 +289,5 @@ func (it *Or) Stats() graph.IteratorStats {
 
 // Register this as an "or" graph.iterator.
 func (it *Or) Type() graph.Type { return graph.Or }
+
+var _ graph.Nexter = &Or{}
diff --git a/graph/iterator/value_comparison_iterator.go b/graph/iterator/value_comparison_iterator.go
index 627b853..b1a0842 100644
--- a/graph/iterator/value_comparison_iterator.go
+++ b/graph/iterator/value_comparison_iterator.go
@@ -218,3 +218,5 @@ func (it *Comparison) Stats() graph.IteratorStats {
 func (it *Comparison) Size() (int64, bool) {
 	return 0, true
 }
+
+var _ graph.Nexter = &Comparison{}
diff --git a/graph/leveldb/all_iterator.go b/graph/leveldb/all_iterator.go
index 515133f..3a118f9 100644
--- a/graph/leveldb/all_iterator.go
+++ b/graph/leveldb/all_iterator.go
@@ -183,3 +183,5 @@ func (it *AllIterator) Stats() graph.IteratorStats {
 		Size:         s,
 	}
 }
+
+var _ graph.Nexter = &AllIterator{}
diff --git a/graph/leveldb/iterator.go b/graph/leveldb/iterator.go
index 6ccd3fe..dcc4aeb 100644
--- a/graph/leveldb/iterator.go
+++ b/graph/leveldb/iterator.go
@@ -283,3 +283,5 @@ func (it *Iterator) Stats() graph.IteratorStats {
 		Size:         s,
 	}
 }
+
+var _ graph.Nexter = &Iterator{}
diff --git a/graph/memstore/all_iterator.go b/graph/memstore/all_iterator.go
index 2d78ead..26cb643 100644
--- a/graph/memstore/all_iterator.go
+++ b/graph/memstore/all_iterator.go
@@ -69,3 +69,6 @@ func (it *quadsAllIterator) Next() bool {
 	}
 	return out
 }
+
+var _ graph.Nexter = &nodesAllIterator{}
+var _ graph.Nexter = &quadsAllIterator{}
diff --git a/graph/memstore/iterator.go b/graph/memstore/iterator.go
index d79e6c8..d93ba62 100644
--- a/graph/memstore/iterator.go
+++ b/graph/memstore/iterator.go
@@ -191,3 +191,5 @@ func (it *Iterator) Stats() graph.IteratorStats {
 		Size:         int64(it.tree.Len()),
 	}
 }
+
+var _ graph.Nexter = &Iterator{}
diff --git a/graph/mongo/iterator.go b/graph/mongo/iterator.go
index 876dff8..bdd3bab 100644
--- a/graph/mongo/iterator.go
+++ b/graph/mongo/iterator.go
@@ -230,3 +230,5 @@ func (it *Iterator) Stats() graph.IteratorStats {
 		Size:         size,
 	}
 }
+
+var _ graph.Nexter = &Iterator{}