diff --git a/lib/propshaft/compiler/source_mapping_urls.rb b/lib/propshaft/compiler/source_mapping_urls.rb
index d15e862..057de24 100644
--- a/lib/propshaft/compiler/source_mapping_urls.rb
+++ b/lib/propshaft/compiler/source_mapping_urls.rb
@@ -11,7 +11,7 @@ def compile(asset, input)
 
   private
     def asset_path(source_mapping_url, logical_path)
-      source_mapping_url.gsub!(/^(.+\/)?#{url_prefix}\//, "")
+      source_mapping_url = ::File.basename(source_mapping_url)
 
       if logical_path.dirname.to_s == "."
         source_mapping_url
diff --git a/test/fixtures/assets/mapped/nested/sourceMappingURL-already-prefixed-nested-with-subdirectory.js b/test/fixtures/assets/mapped/nested/sourceMappingURL-already-prefixed-nested-with-subdirectory.js
new file mode 100644
index 0000000..82bc61b
--- /dev/null
+++ b/test/fixtures/assets/mapped/nested/sourceMappingURL-already-prefixed-nested-with-subdirectory.js
@@ -0,0 +1 @@
+var fun; //# sourceMappingURL=/assets/nested/sourceMappingURL-already-prefixed-nested-with-subdirectory.js.map
diff --git a/test/fixtures/assets/mapped/nested/sourceMappingURL-already-prefixed-nested-with-subdirectory.js.map b/test/fixtures/assets/mapped/nested/sourceMappingURL-already-prefixed-nested-with-subdirectory.js.map
new file mode 100644
index 0000000..e69de29
diff --git a/test/propshaft/compiler/source_mapping_urls_test.rb b/test/propshaft/compiler/source_mapping_urls_test.rb
index ca06d20..f226b94 100644
--- a/test/propshaft/compiler/source_mapping_urls_test.rb
+++ b/test/propshaft/compiler/source_mapping_urls_test.rb
@@ -58,6 +58,8 @@ class Propshaft::Compiler::SourceMappingUrlsTest < ActiveSupport::TestCase
                  compile_asset(find_asset("sourceMappingURL-already-prefixed.js", fixture_path: "mapped"))
     assert_match %r{//# sourceMappingURL=/assets/nested/sourceMappingURL-already-prefixed-nested-[a-z0-9]{8}\.js\.map},
                  compile_asset(find_asset("nested/sourceMappingURL-already-prefixed-nested.js", fixture_path: "mapped"))
+    assert_match %r{//# sourceMappingURL=/assets/nested/sourceMappingURL-already-prefixed-nested-with-subdirectory-[a-z0-9]{8}\.js\.map},
+                 compile_asset(find_asset("nested/sourceMappingURL-already-prefixed-nested-with-subdirectory.js", fixture_path: "mapped"))
   end
 
   test "sourceMapURL is already prefixed with an incorrect url_prefix" do