diff --git a/lib/transformer.js b/lib/transformer.js
index d7a6e73..276bf41 100644
--- a/lib/transformer.js
+++ b/lib/transformer.js
@@ -9,7 +9,7 @@ var pathutils = require('./pathutils'),
     MappedCoverage = require('./mapped').MappedCoverage;
 
 function isInvalidPosition (pos) {
-    return !pos || !pos.line || !pos.column || pos.line < 0 || pos.column < 0;
+    return !pos || typeof pos.line !== "number" || typeof pos.column !== "number" || pos.line < 0 || pos.column < 0;
 }
 
 /**
diff --git a/test/transformer.test.js b/test/transformer.test.js
new file mode 100644
index 0000000..710b4c5
--- /dev/null
+++ b/test/transformer.test.js
@@ -0,0 +1,75 @@
+/* globals describe, it */
+var assert = require('chai').assert,
+    createMap = require('istanbul-lib-coverage').createCoverageMap,
+    SMC = require('source-map').SourceMapConsumer,
+    createTransformer = require('../lib/transformer').create;
+
+function createData() {
+    var sourceMap = {
+        "version": 3,
+        "sources": [
+            "file.js"
+        ],
+        "mappings": ";AAAa,mBAAW,GAAG,MAAM,CAAC;AACrB,kBAAU,GAAG,yBAAyB,CAAC"
+    };
+
+    var coverageData = {
+        "path": "/path/to/file.js",
+        "statementMap": {
+            "1": {
+                "start": {
+                    "line": 2,
+                    "column": 0
+                },
+                "end": {
+                    "line": 2,
+                    "column": 29
+                }
+            },
+            "2": {
+                "start": {
+                    "line": 3,
+                    "column": 0
+                },
+                "end": {
+                    "line": 3,
+                    "column": 47
+                }
+            }
+        },
+        "fnMap": {},
+        "branchMap": {},
+        "s": {
+            "1": 0,
+            "2": 0,
+            "3": 0
+        },
+        "f": {},
+        "b": {}
+    };
+
+    return {
+        sourceMap: sourceMap,
+        coverageData: coverageData
+    };
+}
+
+describe('transformer', function () {
+    it('maps statement locations', function () {
+        var coverageMap = createMap({}),
+            testData = createData(),
+            coverageData = testData.coverageData,
+            sourceMap = testData.sourceMap;
+
+        coverageMap.addFileCoverage(coverageData);
+        var mapped = createTransformer(function() {
+            return new SMC(sourceMap);
+        }).transform(coverageMap);
+
+        assert.deepEqual(mapped.data[coverageData.path].statementMap, {
+            '1': { start: { line: 1, column: 13 }, end: { line: 1, column: 34 } },
+            '2': { start: { line: 2, column: 13 }, end: { line: 2, column: 52 } }
+        });
+    });
+});
+