diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index c50fbdcdd..2dd428d7e 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -2087,16 +2087,13 @@ StorePath EvalState::copyPathToStore(PathSet & context, const SourcePath & path)
     auto dstPath = i != srcToStore.end()
         ? i->second
         : [&]() {
-            #if 0
-            auto p = settings.readOnlyMode
-                ? store->computeStorePathForPath(path2.baseName(), canonPath(path)).first
-                : store->addToStore(path2.baseName(), canonPath(path), FileIngestionMethod::Recursive, htSHA256, defaultPathFilter, repair);
-            #endif
             auto source = sinkToSource([&](Sink & sink) {
                 path.dumpPath(sink);
             });
-            // FIXME: readOnlyMode
-            auto dstPath = store->addToStoreFromDump(*source, path.baseName(), FileIngestionMethod::Recursive, htSHA256, repair);
+            auto dstPath =
+                settings.readOnlyMode
+                ? store->computeStorePathFromDump(*source, path.baseName()).first
+                : store->addToStoreFromDump(*source, path.baseName(), FileIngestionMethod::Recursive, htSHA256, repair);
             allowPath(dstPath);
             srcToStore.insert_or_assign(path, dstPath);
             printMsg(lvlChatty, "copied source '%1%' -> '%2%'", path, store->printStorePath(dstPath));
diff --git a/src/libstore/store-api.cc b/src/libstore/store-api.cc
index 8861274a2..b7b320faf 100644
--- a/src/libstore/store-api.cc
+++ b/src/libstore/store-api.cc
@@ -230,6 +230,19 @@ std::pair<StorePath, Hash> Store::computeStorePathForPath(std::string_view name,
 }
 
 
+std::pair<StorePath, Hash> Store::computeStorePathFromDump(
+    Source & dump,
+    std::string_view name,
+    FileIngestionMethod method,
+    HashType hashAlgo) const
+{
+    HashSink sink(hashAlgo);
+    dump.drainInto(sink);
+    auto hash = sink.finish().first;
+    return {makeFixedOutputPath(method, hash, name), hash};
+}
+
+
 StorePath Store::computeStorePathForText(
     std::string_view name,
     std::string_view s,
diff --git a/src/libstore/store-api.hh b/src/libstore/store-api.hh
index 0c8a4db56..d9681c765 100644
--- a/src/libstore/store-api.hh
+++ b/src/libstore/store-api.hh
@@ -219,10 +219,17 @@ public:
     /* This is the preparatory part of addToStore(); it computes the
        store path to which srcPath is to be copied.  Returns the store
        path and the cryptographic hash of the contents of srcPath. */
+    // FIXME: remove
     std::pair<StorePath, Hash> computeStorePathForPath(std::string_view name,
         const Path & srcPath, FileIngestionMethod method = FileIngestionMethod::Recursive,
         HashType hashAlgo = htSHA256, PathFilter & filter = defaultPathFilter) const;
 
+    std::pair<StorePath, Hash> computeStorePathFromDump(
+        Source & dump,
+        std::string_view name,
+        FileIngestionMethod method = FileIngestionMethod::Recursive,
+        HashType hashAlgo = htSHA256) const;
+
     /* Preparatory part of addTextToStore().
 
        !!! Computation of the path should take the references given to