1 files changed, 1 insertions, 1 deletions
diff --git a/src/libstore/derivations.cc b/src/libstore/derivations.cc
index d9b009d40..becf85245 100644
--- a/src/libstore/derivations.cc
+++ b/src/libstore/derivations.cc
@@ -290,7 +290,7 @@ Hash hashDerivationModulo(Store & store, Derivation drv)
     DerivationInputs inputs2;
     for (auto & i : drv.inputDrvs) {
         Hash h = drvHashes[i.first];
-        if (h.type == htUnknown) {
+        if (!h) {
             assert(store.isValidPath(i.first));
             Derivation drv2 = readDerivation(i.first);
             h = hashDerivationModulo(store, drv2);