diff --git a/lib/sprockets/rails/sourcemapping_url_processor.rb b/lib/sprockets/rails/sourcemapping_url_processor.rb
index fe8a29cc..cd57de66 100644
--- a/lib/sprockets/rails/sourcemapping_url_processor.rb
+++ b/lib/sprockets/rails/sourcemapping_url_processor.rb
@@ -2,7 +2,7 @@ module Sprockets
   module Rails
     # Rewrites source mapping urls with the digested paths and protect against semicolon appending with a dummy comment line
     class SourcemappingUrlProcessor
-      REGEX = /\/\/# sourceMappingURL=(.*\.map)/
+      REGEX = /\/\/# sourceMappingURL=(.*\.map\.?\w*)/
 
       class << self
         def call(input)
diff --git a/test/test_sourcemapping_url_processor.rb b/test/test_sourcemapping_url_processor.rb
index ead7c33a..468655db 100644
--- a/test/test_sourcemapping_url_processor.rb
+++ b/test/test_sourcemapping_url_processor.rb
@@ -46,4 +46,28 @@ def resolve(path, **kargs)
     output = Sprockets::Rails::SourcemappingUrlProcessor.call(input)
     assert_equal({ data: "var mapped;\n" }, output)
   end
+
+  def test_missing_with_json_file_ext_also_removes_file_ext
+    @env.context_class.class_eval do
+      def resolve(path, **kargs)
+        raise Sprockets::FileNotFound
+      end
+    end
+
+    input = { environment: @env, data: "var mapped;\n//# sourceMappingURL=mappedNOT.js.map.json", name: 'mapped', filename: 'mapped.js', metadata: {} }
+    output = Sprockets::Rails::SourcemappingUrlProcessor.call(input)
+    assert_equal({ data: "var mapped;\n" }, output)
+  end
+
+  def test_missing_with_json_file_ext_and_subsequent_valid_js_retains_valid_js
+    @env.context_class.class_eval do
+      def resolve(path, **kargs)
+        raise Sprockets::FileNotFound
+      end
+    end
+
+    input = { environment: @env, data: "var mapped;\n//# sourceMappingURL=mappedNOT.js.map.json\nvar foo = bar();", name: 'mapped', filename: 'mapped.js', metadata: {} }
+    output = Sprockets::Rails::SourcemappingUrlProcessor.call(input)
+    assert_equal({ data: "var mapped;\n\nvar foo = bar();" }, output)
+  end
 end