diff --git a/lib/propshaft/asset.rb b/lib/propshaft/asset.rb
index 6278df0..61582f9 100644
--- a/lib/propshaft/asset.rb
+++ b/lib/propshaft/asset.rb
@@ -42,6 +42,6 @@ def ==(other_asset)
 
   private
     def already_digested?
-      logical_path.to_s =~ /-([0-9a-zA-Z]{7,128})\.digested/
+      logical_path.to_s =~ /-([0-9a-zA-Z_-]{7,128})\.digested/
     end
 end
diff --git a/test/fixtures/assets/first_path/file-already-abcdefVWXYZ0123456789.digested.css b/test/fixtures/assets/first_path/file-already-abcdefVWXYZ0123456789_-.digested.css
similarity index 100%
rename from test/fixtures/assets/first_path/file-already-abcdefVWXYZ0123456789.digested.css
rename to test/fixtures/assets/first_path/file-already-abcdefVWXYZ0123456789_-.digested.css
diff --git a/test/fixtures/assets/first_path/file-already-abcdefVWXYZ0123456789.digested.debug.css b/test/fixtures/assets/first_path/file-already-abcdefVWXYZ0123456789_-.digested.debug.css
similarity index 100%
rename from test/fixtures/assets/first_path/file-already-abcdefVWXYZ0123456789.digested.debug.css
rename to test/fixtures/assets/first_path/file-already-abcdefVWXYZ0123456789_-.digested.debug.css
diff --git a/test/propshaft/asset_test.rb b/test/propshaft/asset_test.rb
index 702a209..a51c10e 100644
--- a/test/propshaft/asset_test.rb
+++ b/test/propshaft/asset_test.rb
@@ -25,18 +25,18 @@ class Propshaft::AssetTest < ActiveSupport::TestCase
     assert find_asset("one.txt").fresh?("f2e1ec14d6856e1958083094170ca6119c529a73")
     assert_not find_asset("one.txt").fresh?("e206c34fe404c8e2f25d60dd8303f61c02b8d381")
 
-    assert find_asset("file-already-abcdefVWXYZ0123456789.digested.css").fresh?(nil)
+    assert find_asset("file-already-abcdefVWXYZ0123456789_-.digested.css").fresh?(nil)
   end
 
   test "digested path" do
     assert_equal "one-f2e1ec14d6856e1958083094170ca6119c529a73.txt",
       find_asset("one.txt").digested_path.to_s
 
-    assert_equal "file-already-abcdefVWXYZ0123456789.digested.css",
-      find_asset("file-already-abcdefVWXYZ0123456789.digested.css").digested_path.to_s
+    assert_equal "file-already-abcdefVWXYZ0123456789_-.digested.css",
+      find_asset("file-already-abcdefVWXYZ0123456789_-.digested.css").digested_path.to_s
 
-    assert_equal "file-already-abcdefVWXYZ0123456789.digested.debug.css",
-      find_asset("file-already-abcdefVWXYZ0123456789.digested.debug.css").digested_path.to_s
+    assert_equal "file-already-abcdefVWXYZ0123456789_-.digested.debug.css",
+      find_asset("file-already-abcdefVWXYZ0123456789_-.digested.debug.css").digested_path.to_s
 
     assert_equal "file-not.digested-e206c34fe404c8e2f25d60dd8303f61c02b8d381.css",
       find_asset("file-not.digested.css").digested_path.to_s
diff --git a/test/propshaft/server_test.rb b/test/propshaft/server_test.rb
index c94a1e3..e213974 100644
--- a/test/propshaft/server_test.rb
+++ b/test/propshaft/server_test.rb
@@ -30,7 +30,7 @@ class Propshaft::ServerTest < ActiveSupport::TestCase
   end
 
   test "serve a predigested file" do
-    asset = @assembly.load_path.find("file-already-abcdefVWXYZ0123456789.digested.css")
+    asset = @assembly.load_path.find("file-already-abcdefVWXYZ0123456789_-.digested.css")
     get "/#{asset.digested_path}"
     assert_equal 200, last_response.status
   end