diff --git a/lix/legacy/dotgraph.cc b/lix/legacy/dotgraph.cc
index 8a22c2892..eec1f0a3a 100644
--- a/lix/legacy/dotgraph.cc
+++ b/lix/legacy/dotgraph.cc
@@ -1,5 +1,6 @@
 #include "dotgraph.hh"
 #include "lix/libstore/store-api.hh"
+#include "lix/libutil/result.hh"
 
 #include <iostream>
 
@@ -41,8 +42,8 @@ static std::string makeNode(std::string_view id, std::string_view label,
 }
 
 
-void printDotGraph(ref<Store> store, StorePathSet && roots)
-{
+kj::Promise<Result<void>> printDotGraph(ref<Store> store, StorePathSet && roots)
+try {
     StorePathSet workList(std::move(roots));
     StorePathSet doneSet;
 
@@ -64,6 +65,9 @@ void printDotGraph(ref<Store> store, StorePathSet && roots)
     }
 
     cout << "}\n";
+    co_return result::success();
+} catch (...) {
+    co_return result::current_exception();
 }
 
 
diff --git a/lix/legacy/dotgraph.hh b/lix/legacy/dotgraph.hh
index ec0fcc9d0..2175ca2d6 100644
--- a/lix/legacy/dotgraph.hh
+++ b/lix/legacy/dotgraph.hh
@@ -5,6 +5,6 @@
 
 namespace nix {
 
-void printDotGraph(ref<Store> store, StorePathSet && roots);
+kj::Promise<Result<void>> printDotGraph(ref<Store> store, StorePathSet && roots);
 
 }
diff --git a/lix/legacy/graphml.cc b/lix/legacy/graphml.cc
index c67d6a204..5cb4f6bc0 100644
--- a/lix/legacy/graphml.cc
+++ b/lix/legacy/graphml.cc
@@ -1,6 +1,7 @@
 #include "graphml.hh"
 #include "lix/libstore/store-api.hh"
 #include "lix/libstore/derivations.hh"
+#include "lix/libutil/result.hh"
 
 #include <iostream>
 
@@ -46,8 +47,8 @@ static std::string makeNode(const ValidPathInfo & info)
 }
 
 
-void printGraphML(ref<Store> store, StorePathSet && roots)
-{
+kj::Promise<Result<void>> printGraphML(ref<Store> store, StorePathSet && roots)
+try {
     StorePathSet workList(std::move(roots));
     StorePathSet doneSet;
     std::pair<StorePathSet::iterator, bool> ret;
@@ -81,6 +82,9 @@ void printGraphML(ref<Store> store, StorePathSet && roots)
 
     cout << "</graph>\n";
     cout << "</graphml>\n";
+    co_return result::success();
+} catch (...) {
+    co_return result::current_exception();
 }
 
 
diff --git a/lix/legacy/graphml.hh b/lix/legacy/graphml.hh
index e8c84bea3..48e04fe41 100644
--- a/lix/legacy/graphml.hh
+++ b/lix/legacy/graphml.hh
@@ -5,6 +5,6 @@
 
 namespace nix {
 
-void printGraphML(ref<Store> store, StorePathSet && roots);
+kj::Promise<Result<void>> printGraphML(ref<Store> store, StorePathSet && roots);
 
 }
diff --git a/lix/legacy/nix-store.cc b/lix/legacy/nix-store.cc
index 6dbeecef7..f1ce0298e 100644
--- a/lix/legacy/nix-store.cc
+++ b/lix/legacy/nix-store.cc
@@ -429,7 +429,7 @@ static void opQuery(AsyncIoRoot & aio, Strings opFlags, Strings opArgs)
             for (auto & i : opArgs)
                 for (auto & j : aio.blockOn(maybeUseOutputs(store->followLinksToStorePath(i), useOutput, forceRealise)))
                     roots.insert(j);
-            printDotGraph(ref<Store>(store), std::move(roots));
+            aio.blockOn(printDotGraph(ref<Store>(store), std::move(roots)));
             break;
         }
 
@@ -438,7 +438,7 @@ static void opQuery(AsyncIoRoot & aio, Strings opFlags, Strings opArgs)
             for (auto & i : opArgs)
                 for (auto & j : aio.blockOn(maybeUseOutputs(store->followLinksToStorePath(i), useOutput, forceRealise)))
                     roots.insert(j);
-            printGraphML(ref<Store>(store), std::move(roots));
+            aio.blockOn(printGraphML(ref<Store>(store), std::move(roots)));
             break;
         }