diff --git a/src/system/Error.hxx b/src/system/Error.hxx
index a94678872..92c638f4f 100644
--- a/src/system/Error.hxx
+++ b/src/system/Error.hxx
@@ -147,6 +147,14 @@ FormatErrno(const char *fmt, Args&&... args) noexcept
 	return FormatErrno(errno, fmt, std::forward<Args>(args)...);
 }
 
+gcc_pure
+inline bool
+IsErrno(const std::system_error &e, int code) noexcept
+{
+	return e.code().category() == ErrnoCategory() &&
+		e.code().value() == code;
+}
+
 gcc_pure
 static inline bool
 IsFileNotFound(const std::system_error &e) noexcept
@@ -155,8 +163,7 @@ IsFileNotFound(const std::system_error &e) noexcept
 	return e.code().category() == std::system_category() &&
 		e.code().value() == ERROR_FILE_NOT_FOUND;
 #else
-	return e.code().category() == ErrnoCategory() &&
-		e.code().value() == ENOENT;
+	return IsErrno(e, ENOENT);
 #endif
 }
 
@@ -168,8 +175,7 @@ IsPathNotFound(const std::system_error &e) noexcept
 	return e.code().category() == std::system_category() &&
 		e.code().value() == ERROR_PATH_NOT_FOUND;
 #else
-	return e.code().category() == ErrnoCategory() &&
-		e.code().value() == ENOTDIR;
+	return IsErrno(e, ENOTDIR);
 #endif
 }
 
@@ -181,8 +187,7 @@ IsAccessDenied(const std::system_error &e) noexcept
 	return e.code().category() == std::system_category() &&
 		e.code().value() == ERROR_ACCESS_DENIED;
 #else
-	return e.code().category() == ErrnoCategory() &&
-		e.code().value() == EACCES;
+	return IsErrno(e, EACCES);
 #endif
 }