diff --git a/src/nix/cat.cc b/src/nix/cat.cc
index 5b93d560b..1284b50fd 100644
--- a/src/nix/cat.cc
+++ b/src/nix/cat.cc
@@ -76,6 +76,8 @@ struct CmdCatNar : StoreCommand, MixCat
     void run(ref<Store> store) override
     {
         AutoCloseFD fd = open(narPath.c_str(), O_RDONLY);
+        if (!fd)
+            throw SysError("opening NAR file '%s'", narPath);
         auto source = FdSource{fd.get()};
         auto narAccessor = makeNarAccessor(source);
         auto listing = listNar(narAccessor, CanonPath::root, true);
diff --git a/src/nix/ls.cc b/src/nix/ls.cc
index 846af246d..82721222e 100644
--- a/src/nix/ls.cc
+++ b/src/nix/ls.cc
@@ -146,6 +146,8 @@ struct CmdLsNar : Command, MixLs
     void run() override
     {
         AutoCloseFD fd = open(narPath.c_str(), O_RDONLY);
+        if (!fd)
+            throw SysError("opening NAR file '%s'", narPath);
         auto source = FdSource{fd.get()};
         auto narAccessor = makeNarAccessor(source);
         auto listing = listNar(narAccessor, CanonPath::root, true);