diff --git a/src/raven.js b/src/raven.js
index b099d2a7dfbc..7a2f79474ddb 100644
--- a/src/raven.js
+++ b/src/raven.js
@@ -644,12 +644,14 @@ function joinRegExp(patterns) {
     // Be mad.
     var sources = [], i = patterns.length;
     while (i--) {
-        sources[i] = isString(patterns[i]) ?
-            // If it's a string, we need to escape it
-            // Taken from: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions
-            patterns[i].replace(/([.*+?^=!:${}()|\[\]\/\\])/g, "\\$1") :
-            // If it's a regexp already, we want to extract the source
-            patterns[i].source;
+        if (!isUndefined(patterns[i]) && patterns[i]) {
+            sources[i] = isString(patterns[i]) ?
+                // If it's a string, we need to escape it
+                // Taken from: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions
+                patterns[i].replace(/([.*+?^=!:${}()|\[\]\/\\])/g, "\\$1") :
+                // If it's a regexp already, we want to extract the source
+                patterns[i].source;
+        }
     }
     return new RegExp(sources.join('|'), 'i');
 }
diff --git a/test/raven.test.js b/test/raven.test.js
index 67c605ff7408..14736ffad69c 100644
--- a/test/raven.test.js
+++ b/test/raven.test.js
@@ -873,6 +873,12 @@ describe('globals', function() {
                 'a', 'b', 'a.b', /d/, /[0-9]/
             ]).source, 'a|b|a\\.b|d|[0-9]');
         });
+        
+        it('should not process empty or undefined variables', function() {
+            assert.equal(joinRegExp([
+                'a', 'b', null, undefined
+            ]).source, 'a|b');
+        });
     });
 });