diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index c1dadcd84..f003685c2 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -585,16 +585,16 @@ static void canonicalisePathMetaData_(const Path & path, uid_t fromUid, InodesSe
 
     if (eaSize < 0) {
         if (errno != ENOTSUP)
-            throw SysError("querying extended attributes of ‘%s’", path);
+            throw SysError(format("querying extended attributes of ‘%s’") % path);
     } else if (eaSize > 0) {
         std::vector<char> eaBuf(eaSize);
 
         if ((eaSize = llistxattr(path.c_str(), eaBuf.data(), eaBuf.size())) < 0)
-            throw SysError("querying extended attributes of ‘%s’", path);
+            throw SysError(format("querying extended attributes of ‘%s’") % path);
 
         for (auto & eaName: tokenizeString<Strings>(std::string(eaBuf.data(), eaSize), std::string("\000", 1)))
             if (lremovexattr(path.c_str(), eaName.c_str()) == -1)
-                throw SysError("removing extended attribute ‘%s’ from ‘%s’", eaName, path);
+                throw SysError(format("removing extended attribute ‘%s’ from ‘%s’") % eaName % path);
     }
 #endif