diff --git a/lib/minify.js b/lib/minify.js
index d84f6825..39e2979c 100644
--- a/lib/minify.js
+++ b/lib/minify.js
@@ -8,7 +8,7 @@ var to_base64 = typeof btoa == "undefined" ? function(str) {
 } : btoa;
 
 function read_source_map(name, code) {
-    var match = /\n\/\/# sourceMappingURL=data:application\/json(;.*?)?;base64,(.*)/.exec(code);
+    var match = /(?:^|[^.])\/\/# sourceMappingURL=data:application\/json(;[\w=-]*)?;base64,([+/0-9A-Za-z]*=*)\s*$/.exec(code);
     if (!match) {
         AST_Node.warn("inline source map not found: " + name);
         return null;