diff --git a/index.ts b/index.ts
index 29f5370..a0a51b8 100644
--- a/index.ts
+++ b/index.ts
@@ -69,12 +69,22 @@ module tss {
                 getScriptVersion: (fileName) => this.files[fileName] && this.files[fileName].version.toString(),
                 getScriptSnapshot: (fileName) => {
                     var file = this.files[fileName];
-                    return {
-                        getText: (start, end) => file.text.substring(start, end),
-                        getLength: () => file.text.length,
-                        getLineStartPositions: () => [],
-                        getChangeRange: (oldSnapshot) => undefined
-                    };
+                    if (file) {
+                        return {
+                            getText: (start, end) => file.text.substring(start, end),
+                            getLength: () => file.text.length,
+                            getLineStartPositions: (): number[]=> [],
+                            getChangeRange: (oldSnapshot) => undefined
+                        };
+                    }
+                    else { // This is some reference import
+                        return {
+                            getText: (start, end) => '',
+                            getLength: () => 0,
+                            getLineStartPositions: (): number[]=> [],
+                            getChangeRange: (oldSnapshot) => undefined
+                        };
+                    }
                 },
                 getCurrentDirectory: () => process.cwd(),
                 getScriptIsOpen: () => true,
diff --git a/test/test.js b/test/test.js
index 6d1ac4f..ec89677 100644
--- a/test/test.js
+++ b/test/test.js
@@ -86,6 +86,14 @@ describe('typescript-update', function() {
             var expected = "var x = 'some string';" + eol;
             assert.equal(tss.compile(src), expected);
         });
+        
+        it('reference imports are ignored', function() {
+            var src = "/// <reference path='./typings/tsd'/>" + eol
+                    + "var x: number = 'some string';";
+            var expected = "/// <reference path='./typings/tsd'/>" + eol
+                    + "var x = 'some string';" + eol;
+            assert.equal(tss.compile(src), expected);
+        });
 
         it('syntactic errors are not ignored', function() {
             var src = "var x = 123 123;";