1 files changed, 4 insertions, 0 deletions
diff --git a/node_modules/istanbul-lib-coverage/lib/file.js b/node_modules/istanbul-lib-coverage/lib/file.js
index 0cfb8a4be..3cb0ce263 100644
--- a/node_modules/istanbul-lib-coverage/lib/file.js
+++ b/node_modules/istanbul-lib-coverage/lib/file.js
@@ -250,6 +250,10 @@ FileCoverage.prototype.merge = function (other) {
         var i,
             retArray = that.data.b[k],
             secondArray = other.b[k];
+        if (!retArray) {
+            that.data.b[k] = secondArray;
+            return;
+        }
         for (i = 0; i < retArray.length; i += 1) {
             retArray[i] += secondArray[i];
         }