diff --git a/src/adapters/custom.rs b/src/adapters/custom.rs
index 9d15557..e02f979 100644
--- a/src/adapters/custom.rs
+++ b/src/adapters/custom.rs
@@ -50,103 +50,32 @@ impl Default for CustomIdentifiers {
     fn default() -> CustomIdentifiers {
         CustomIdentifiers {
             ffmpeg: CustomIdentifier {
-                extensions: Some(
-                    ffmpeg::EXTENSIONS
-                        .iter()
-                        .map(|&s| s.to_string())
-                        .collect::<Vec<String>>(),
-                ),
-                mimetypes: Some(
-                    ffmpeg::MIMETYPES
-                        .to_vec()
-                        .iter()
-                        .map(|&s| s.to_string())
-                        .collect::<Vec<String>>(),
-                ),
+                extensions: Some(strs(ffmpeg::EXTENSIONS)),
+                mimetypes: Some(strs(ffmpeg::MIMETYPES)),
             },
             gz: CustomIdentifier {
-                extensions: Some(
-                    decompress::EXTENSIONS_GZ
-                        .iter()
-                        .map(|&s| s.to_string())
-                        .collect::<Vec<String>>(),
-                ),
-                mimetypes: Some(
-                    decompress::MIMETYPES_GZ
-                        .iter()
-                        .map(|&s| s.to_string())
-                        .collect::<Vec<String>>(),
-                ),
+                extensions: Some(strs(decompress::EXTENSIONS_GZ)),
+                mimetypes: Some(strs(decompress::MIMETYPES_GZ)),
             },
             bz2: CustomIdentifier {
-                extensions: Some(
-                    decompress::EXTENSIONS_BZ2
-                        .iter()
-                        .map(|&s| s.to_string())
-                        .collect::<Vec<String>>(),
-                ),
-                mimetypes: Some(
-                    decompress::MIMETYPES_BZ2
-                        .iter()
-                        .map(|&s| s.to_string())
-                        .collect::<Vec<String>>(),
-                ),
+                extensions: Some(strs(decompress::EXTENSIONS_BZ2)),
+                mimetypes: Some(strs(decompress::MIMETYPES_BZ2)),
             },
             xz: CustomIdentifier {
-                extensions: Some(
-                    decompress::EXTENSIONS_XZ
-                        .iter()
-                        .map(|&s| s.to_string())
-                        .collect::<Vec<String>>(),
-                ),
-                mimetypes: Some(
-                    decompress::MIMETYPES_XZ
-                        .iter()
-                        .map(|&s| s.to_string())
-                        .collect::<Vec<String>>(),
-                ),
+                extensions: Some(strs(decompress::EXTENSIONS_XZ)),
+                mimetypes: Some(strs(decompress::MIMETYPES_XZ)),
             },
             zst: CustomIdentifier {
-                extensions: Some(
-                    decompress::EXTENSIONS_ZST
-                        .iter()
-                        .map(|&s| s.to_string())
-                        .collect::<Vec<String>>(),
-                ),
-                mimetypes: Some(
-                    decompress::MIMETYPES_ZST
-                        .iter()
-                        .map(|&s| s.to_string())
-                        .collect::<Vec<String>>(),
-                ),
+                extensions: Some(strs(decompress::EXTENSIONS_ZST)),
+                mimetypes: Some(strs(decompress::MIMETYPES_ZST)),
             },
             zip: CustomIdentifier {
-                extensions: Some(
-                    zip::EXTENSIONS
-                        .iter()
-                        .map(|&s| s.to_string())
-                        .collect::<Vec<String>>(),
-                ),
-                mimetypes: Some(
-                    zip::MIMETYPES
-                        .iter()
-                        .map(|&s| s.to_string())
-                        .collect::<Vec<String>>(),
-                ),
+                extensions: Some(strs(zip::EXTENSIONS)),
+                mimetypes: Some(strs(zip::MIMETYPES)),
             },
             mbox: CustomIdentifier {
-                extensions: Some(
-                    mbox::EXTENSIONS
-                        .iter()
-                        .map(|&s| s.to_string())
-                        .collect::<Vec<String>>(),
-                ),
-                mimetypes: Some(
-                    mbox::MIMETYPES
-                        .iter()
-                        .map(|&s| s.to_string())
-                        .collect::<Vec<String>>(),
-                ),
+                extensions: Some(strs(mbox::EXTENSIONS)),
+                mimetypes: Some(strs(mbox::MIMETYPES)),
             },
         }
     }