diff --git a/common/modules/base.jsm b/common/modules/base.jsm
index 39541950..fe67024f 100644
--- a/common/modules/base.jsm
+++ b/common/modules/base.jsm
@@ -1444,7 +1444,7 @@ function UTF8(str) {
     }
 }
 
-function octal(decimal) parseInt(decimal, 8);
+var octal = deprecated("octal integer literals", function octal(decimal) parseInt(decimal, 8));
 
 /**
  * Iterates over an arbitrary object. The following iterator types are
diff --git a/common/modules/buffer.jsm b/common/modules/buffer.jsm
index ac11c4e0..18319c46 100644
--- a/common/modules/buffer.jsm
+++ b/common/modules/buffer.jsm
@@ -747,7 +747,7 @@ var Buffer = Module("Buffer", {
 
                     try {
                         if (!file.exists())
-                            file.create(File.NORMAL_FILE_TYPE, octal(644));
+                            file.create(File.NORMAL_FILE_TYPE, 0o644);
                     }
                     catch (e) {
                         util.assert(false, _("save.invalidDestination", e.name));
@@ -784,7 +784,7 @@ var Buffer = Module("Buffer", {
         let privacy = sanitizer.getContext(params.context || this.win);
         let file = File(params.file);
         if (!file.exists())
-            file.create(Ci.nsIFile.NORMAL_FILE_TYPE, octal(666));
+            file.create(Ci.nsIFile.NORMAL_FILE_TYPE, 0o666);
 
         let downloadListener = new window.DownloadListener(window,
                 services.Transfer(params.uri, file.URI, "", null, null, null,
diff --git a/common/modules/cache.jsm b/common/modules/cache.jsm
index fc045954..398d3c9d 100644
--- a/common/modules/cache.jsm
+++ b/common/modules/cache.jsm
@@ -79,7 +79,7 @@ var Cache = Module("Cache", XPCOM(Ci.nsIRequestObserver), {
         let dir = File(services.directory.get("ProfD", Ci.nsIFile))
                     .child("dactyl");
         if (!dir.exists())
-            dir.create(dir.DIRECTORY_TYPE, octal(777));
+            dir.create(dir.DIRECTORY_TYPE, 0o777);
         return dir.child("cache.zip");
     }),
 
diff --git a/common/modules/help.jsm b/common/modules/help.jsm
index f3a7b32c..3a1f5350 100644
--- a/common/modules/help.jsm
+++ b/common/modules/help.jsm
@@ -287,7 +287,7 @@ var Help = Module("Help", {
             const TIME = Date.now();
 
             if (!FILE.exists() && (/\/$/.test(path) && !/\./.test(FILE.leafName)))
-                FILE.create(FILE.DIRECTORY_TYPE, octal(755));
+                FILE.create(FILE.DIRECTORY_TYPE, 0o755);
 
             dactyl.initHelp();
             if (FILE.isDirectory()) {
diff --git a/common/modules/io.jsm b/common/modules/io.jsm
index 24fae9a3..b0466dc2 100644
--- a/common/modules/io.jsm
+++ b/common/modules/io.jsm
@@ -322,7 +322,7 @@ var IO = Module("io", {
     createTempFile: function createTempFile(ext="txt", label="") {
         let file = services.directory.get("TmpD", Ci.nsIFile);
         file.append(config.name + label + "." + ext);
-        file.createUnique(Ci.nsIFile.NORMAL_FILE_TYPE, octal(666));
+        file.createUnique(Ci.nsIFile.NORMAL_FILE_TYPE, 0o666);
 
         services.externalApp.deleteTemporaryFileOnExit(file);
 
diff --git a/common/modules/storage.jsm b/common/modules/storage.jsm
index 5ff94561..5420564d 100644
--- a/common/modules/storage.jsm
+++ b/common/modules/storage.jsm
@@ -544,7 +544,7 @@ var File = Class("File", {
             mode = File.MODE_WRONLY | File.MODE_CREATE | File.MODE_TRUNCATE;
 
         if (!perms)
-            perms = octal(644);
+            perms = 0o644;
         if (!this.exists()) // OCREAT won't create the directory
             this.create(this.NORMAL_FILE_TYPE, perms);