diff --git a/src/js/background.js b/src/js/background.js
index ef06a8c97..04f2d7fb8 100644
--- a/src/js/background.js
+++ b/src/js/background.js
@@ -139,7 +139,7 @@ var µBlock = (function() { // jshint ignore:line
 
         // Read-only
         systemSettings: {
-            compiledMagic: 3,   // Increase when compiled format changes
+            compiledMagic: 4,   // Increase when compiled format changes
             selfieMagic: 4      // Increase when selfie format changes
         },
 
diff --git a/src/js/scriptlet-filtering.js b/src/js/scriptlet-filtering.js
index 52fc700f3..404243417 100644
--- a/src/js/scriptlet-filtering.js
+++ b/src/js/scriptlet-filtering.js
@@ -1,7 +1,7 @@
 /*******************************************************************************
 
     uBlock Origin - a browser extension to block requests.
-    Copyright (C) 2017-2018 Raymond Hill
+    Copyright (C) 2017-present Raymond Hill
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -216,7 +216,7 @@
             'cosmetic',
             {
                 source: 'cosmetic',
-                raw: (isException ? '#@#' : '##') + 'script:inject(' + token + ')'
+                raw: (isException ? '#@#' : '##') + '+js(' + token + ')'
             },
             'dom',
             details.url,
@@ -253,14 +253,14 @@
         //   Ignore instances of exception filter with negated hostnames,
         //   because there is no way to create an exception to an exception.
 
-        var µburi = µb.URI;
+        let µburi = µb.URI;
 
-        for ( var hostname of parsed.hostnames ) {
-            var negated = hostname.charCodeAt(0) === 0x7E /* '~' */;
+        for ( let hostname of parsed.hostnames ) {
+            let negated = hostname.charCodeAt(0) === 0x7E /* '~' */;
             if ( negated ) {
                 hostname = hostname.slice(1);
             }
-            var hash = µburi.domainFromHostname(hostname);
+            let hash = µburi.domainFromHostname(hostname);
             if ( parsed.exception ) {
                 if ( negated ) { continue; }
                 hash = '!' + hash;
@@ -272,9 +272,9 @@
     };
 
     // 01234567890123456789
-    // script:inject(token[, arg[, ...]])
-    //               ^                 ^
-    //              14                 -1
+    // +js(token[, arg[, ...]])
+    //     ^                 ^
+    //     4                -1
 
     api.fromCompiledContent = function(reader) {
         // 1001 = scriptlet injection
@@ -282,17 +282,17 @@
 
         while ( reader.next() ) {
             acceptedCount += 1;
-            var fingerprint = reader.fingerprint();
+            let fingerprint = reader.fingerprint();
             if ( duplicates.has(fingerprint) ) {
                 discardedCount += 1;
                 continue;
             }
             duplicates.add(fingerprint);
-            var args = reader.args();
+            let args = reader.args();
             if ( args.length < 4 ) { continue; }
             scriptletDB.add(
                 args[1],
-                { hostname: args[2], token: args[3].slice(14, -1) }
+                { hostname: args[2], token: args[3].slice(4, -1) }
             );
         }
     };
diff --git a/src/js/static-ext-filtering.js b/src/js/static-ext-filtering.js
index 94f38a741..ceaa16fc2 100644
--- a/src/js/static-ext-filtering.js
+++ b/src/js/static-ext-filtering.js
@@ -603,9 +603,9 @@
     })();
 
     api.compile = function(raw, writer) {
-        var lpos = raw.indexOf('#');
+        let lpos = raw.indexOf('#');
         if ( lpos === -1 ) { return false; }
-        var rpos = lpos + 1;
+        let rpos = lpos + 1;
         if ( raw.charCodeAt(rpos) !== 0x23 /* '#' */ ) {
             rpos = raw.indexOf('#', rpos + 1);
             if ( rpos === -1 ) { return false; }
@@ -618,7 +618,7 @@
         if ( (rpos - lpos) > 3 ) { return false; }
 
         // Extract the selector.
-        var suffix = raw.slice(rpos + 1).trim();
+        let suffix = raw.slice(rpos + 1).trim();
         if ( suffix.length === 0 ) { return false; }
         parsed.suffix = suffix;
 
@@ -629,7 +629,7 @@
         //   We have an Adguard/ABP cosmetic filter if and only if the
         //   character is `$`, `%` or `?`, otherwise it's not a cosmetic
         //   filter.
-        var cCode = raw.charCodeAt(rpos - 1);
+        let cCode = raw.charCodeAt(rpos - 1);
         if ( cCode !== 0x23 /* '#' */ && cCode !== 0x40 /* '@' */ ) {
             // Adguard's scriptlet injection: not supported.
             if ( cCode === 0x25 /* '%' */ ) { return true; }
@@ -652,37 +652,26 @@
         if ( lpos === 0 ) {
             parsed.hostnames = emptyArray;
         } else {
-            var prefix = raw.slice(0, lpos);
+            let prefix = raw.slice(0, lpos);
             parsed.hostnames = prefix.split(reHostnameSeparator);
             if ( reHasUnicode.test(prefix) ) {
                 toASCIIHostnames(parsed.hostnames);
             }
         }
 
+        // Backward compatibility with deprecated syntax.
         if ( suffix.startsWith('script:') ) {
-            // Scriptlet injection engine.
             if ( suffix.startsWith('script:inject') ) {
-                µb.scriptletFilteringEngine.compile(parsed, writer);
-                return true;
-            }
-            // Script tag filtering: courtesy-conversion to HTML filtering.
-            if ( suffix.startsWith('script:contains') ) {
-                console.info(
-                    'uBO: ##script:contains(...) is deprecated, ' +
-                    'converting to ##^script:has-text(...)'
-                );
-                suffix = suffix.replace(/^script:contains/, '^script:has-text');
-                parsed.suffix = suffix;
+                suffix = parsed.suffix = '+js' + suffix.slice(13);
+            } else if ( suffix.startsWith('script:contains') ) {
+                suffix = parsed.suffix = '^script:has-text' + suffix.slice(15);
             }
         }
 
-        var c0 = suffix.charCodeAt(0);
+        let c0 = suffix.charCodeAt(0);
 
         // New shorter syntax for scriptlet injection engine.
         if ( c0 === 0x2B /* '+' */ && suffix.startsWith('+js') ) {
-            // Convert to deprecated syntax for now. Once 1.15.12 is
-            // widespread, `+js` form will be the official syntax.
-            parsed.suffix = 'script:inject' + parsed.suffix.slice(3);
             µb.scriptletFilteringEngine.compile(parsed, writer);
             return true;
         }