diff --git a/python/servo/mutation/test.py b/python/servo/mutation/test.py
index 39c5c84903ad..242d545a305d 100644
--- a/python/servo/mutation/test.py
+++ b/python/servo/mutation/test.py
@@ -33,28 +33,32 @@ def mutate_random_line(file_name):
 
 
 def mutation_test(file_name, tests):
-    mutated_line = mutate_random_line(file_name)
-    if mutated_line != -1:
-        print "Mutating {0} at line {1}".format(file_name, mutated_line)
-        print "compling mutant {0}:{1}".format(file_name, mutated_line)
-        sys.stdout.flush()
-        subprocess.call('python mach build --release', shell=True, stdout=DEVNULL)
-        for test in tests:
-            test_command = "python mach test-wpt {0} --release".format(test.encode('utf-8'))
-            print "running `{0}` test for mutant {1}:{2}".format(test, file_name, mutated_line)
+    local_changes_present = subprocess.call('git diff --quiet {0}'.format(file_name), shell=True)
+    if local_changes_present == 1:
+        print "{0} has local changes, please commit/remove changes before running the test".format(file_name)
+    else:
+        mutated_line = mutate_random_line(file_name)
+        if mutated_line != -1:
+            print "Mutating {0} at line {1}".format(file_name, mutated_line)
+            print "compling mutant {0}:{1}".format(file_name, mutated_line)
             sys.stdout.flush()
-            test_status = subprocess.call(test_command, shell=True, stdout=DEVNULL)
-            if test_status != 0:
-                print("Failed: while running `{0}`".format(test_command))
-                print "mutated file {0} diff".format(file_name)
+            subprocess.call('python mach build --release', shell=True, stdout=DEVNULL)
+            for test in tests:
+                test_command = "python mach test-wpt {0} --release".format(test.encode('utf-8'))
+                print "running `{0}` test for mutant {1}:{2}".format(test, file_name, mutated_line)
                 sys.stdout.flush()
-                subprocess.call('git --no-pager diff {0}'.format(file_name), shell=True)
-            else:
-                print("Success: Mutation killed by {0}".format(test.encode('utf-8')))
-                break
-        print "reverting mutant {0}:{1}".format(file_name, mutated_line)
-        sys.stdout.flush()
-        subprocess.call('git checkout {0}'.format(file_name), shell=True)
-    else:
-        print "Cannot mutate {0}".format(file_name)
-    print "-----------------------------------------------------------------\n"
+                test_status = subprocess.call(test_command, shell=True, stdout=DEVNULL)
+                if test_status != 0:
+                    print("Failed: while running `{0}`".format(test_command))
+                    print "mutated file {0} diff".format(file_name)
+                    sys.stdout.flush()
+                    subprocess.call('git --no-pager diff {0}'.format(file_name), shell=True)
+                else:
+                    print("Success: Mutation killed by {0}".format(test.encode('utf-8')))
+                    break
+            print "reverting mutant {0}:{1}".format(file_name, mutated_line)
+            sys.stdout.flush()
+            subprocess.call('git checkout {0}'.format(file_name), shell=True)
+        else:
+            print "Cannot mutate {0}".format(file_name)
+        print "-----------------------------------------------------------------\n"