diff --git a/src/Controls.js b/src/Controls.js
index 3801d09f..c6a9879d 100644
--- a/src/Controls.js
+++ b/src/Controls.js
@@ -14,8 +14,7 @@ var Controls = React.createClass({
     // XXX: can we be more specific than this with Flow?
     onChange: React.PropTypes.func.isRequired
   },
-  makeRange: function() {
-    // XXX Removing the Number() should lead to type errors, but doesn't.
+  makeRange: function(): GenomeRange {
     return {
       contig: this.refs.contig.getDOMNode().value,
       start: Number(this.refs.start.getDOMNode().value),
@@ -35,8 +34,10 @@ var Controls = React.createClass({
     this.refs.start.getDOMNode().value = r.start;
     this.refs.stop.getDOMNode().value = r.stop;
 
-    var contigIdx = this.props.contigList.indexOf(r.contig);
-    this.refs.contig.getDOMNode().selectedIndex = contigIdx;
+    if (this.props.contigList) {
+      var contigIdx = this.props.contigList.indexOf(r.contig);
+      this.refs.contig.getDOMNode().selectedIndex = contigIdx;
+    }
   },
   render: function(): any {
     var contigOptions = this.props.contigList
@@ -56,7 +57,7 @@ var Controls = React.createClass({
       </form>
     );
   },
-  componentDidUpdate: function(prevProps, prevState) {
+  componentDidUpdate: function(prevProps: Object) {
     if (!_.isEqual(prevProps.range, this.props.range)) {
       this.updateRangeUI();
     }
diff --git a/src/TwoBit.js b/src/TwoBit.js
index 1979e50f..d8552e7c 100644
--- a/src/TwoBit.js
+++ b/src/TwoBit.js
@@ -37,7 +37,6 @@ type SequenceRecord = {
 
 type TwoBitHeader = {
   sequenceCount: number;
-  reserved: number;
   sequences: Array<FileIndexEntry>;
 }
 
diff --git a/types/types.js b/types/types.js
index 5daabf22..3357c71d 100644
--- a/types/types.js
+++ b/types/types.js
@@ -1,5 +1,5 @@
 declare class GenomeRange {
   contig: string;
-  start: number;
-  stop: number;  // XXX inclusive or exclusive?
+  start: number;  // inclusive
+  stop: number;  // inclusive
 }