diff --git a/src/main/json/GA4GHVariantJson.js b/src/main/json/GA4GHVariantJson.js
index 1ac736f8..d2763b07 100644
--- a/src/main/json/GA4GHVariantJson.js
+++ b/src/main/json/GA4GHVariantJson.js
@@ -24,7 +24,9 @@ function create(json: string): VcfDataSource {
   // fill variants with json
   if (!_.isEmpty(parsedJson)) {
       variants = _.values(parsedJson.variants).map(variant => new VariantContext(Variant.fromGA4GH(variant),variant.calls));
-      callSetNames = _.map(variants[0].calls, c => c.callSetName);
+      if (variants.length > 0) { // only call variants if non-empty
+          callSetNames = _.map(variants[0].calls, c => c.callSetName);
+      }
   }
 
   function rangeChanged(newRange: GenomeRange) {
diff --git a/src/test/json/GA4GHVariantJson-test.js b/src/test/json/GA4GHVariantJson-test.js
index c211033b..d18cb275 100644
--- a/src/test/json/GA4GHVariantJson-test.js
+++ b/src/test/json/GA4GHVariantJson-test.js
@@ -17,7 +17,7 @@ describe('GA4GHVariantJson', function() {
   });
 
   it('should filter variants from json', function(done) {
-    
+
     var source = GA4GHVariantJson.create(json);
 
     var requestInterval = new ContigInterval('1', 10000, 10500);
@@ -62,4 +62,16 @@ describe('GA4GHVariantJson', function() {
 
   });
 
+  it('should not fail when there are no variants', function(done) {
+
+    var source = GA4GHVariantJson.create("{\"variants\": []}");
+
+    var requestInterval = new ContigInterval('1', 10, 20);
+
+    var variants = source.getVariantsInRange(requestInterval);
+    expect(variants).to.have.length(0);
+    done();
+
+  });
+
 });