diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 74a7162ffa3..a097bae9f91 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -579,6 +579,12 @@ public:
        `Opaque` element of that store path. */
     void mkStorePathString(const StorePath & storePath, Value & v);
 
+    /* Parsing a string as a store path.
+
+       The string should be the same (string itself and context) as a call to
+       `mkStorePathString` on the returned store path. */
+    StorePath parseStorePathString(const Value & v);
+
     void concatLists(Value & v, size_t nrLists, Value * * lists, const PosIdx pos, std::string_view errorCtx);
 
     /**