diff --git a/src/libstore/build/derivation-building-goal.cc b/src/libstore/build/derivation-building-goal.cc
index e8df06564..a15f6f35f 100644
--- a/src/libstore/build/derivation-building-goal.cc
+++ b/src/libstore/build/derivation-building-goal.cc
@@ -1304,6 +1304,7 @@ SingleDrvOutputs DerivationBuildingGoal::assertPathValidity()
 
 Goal::Done DerivationBuildingGoal::doneSuccess(BuildResult::Status status, SingleDrvOutputs builtOutputs)
 {
+    outputLocks.unlock();
     buildResult.status = status;
 
     assert(buildResult.success());
@@ -1321,6 +1322,7 @@ Goal::Done DerivationBuildingGoal::doneSuccess(BuildResult::Status status, Singl
 
 Goal::Done DerivationBuildingGoal::doneFailure(BuildError ex)
 {
+    outputLocks.unlock();
     buildResult.status = ex.status;
     buildResult.errorMsg = fmt("%s", Uncolored(ex.info().msg));
     if (buildResult.status == BuildResult::TimedOut)