diff --git a/src/libcmd/installables.cc b/src/libcmd/installables.cc
index d2600ca91fd8..b5675d5bd17c 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -931,10 +931,7 @@ std::vector<std::pair<std::shared_ptr<Installable>, BuiltPathWithResult>> Instal
                                 DrvOutput outputId { *outputHash, output };
                                 auto realisation = store->queryRealisation(outputId);
                                 if (!realisation)
-                                    throw Error(
-                                        "cannot operate on an output of the "
-                                        "unbuilt derivation '%s'",
-                                        outputId.to_string());
+                                    throw MissingRealisation(outputId);
                                 outputs.insert_or_assign(output, realisation->outPath);
                             } else {
                                 // If ca-derivations isn't enabled, assume that
diff --git a/src/libstore/realisation.hh b/src/libstore/realisation.hh
index 9070a6ee21d4..911c619095a9 100644
--- a/src/libstore/realisation.hh
+++ b/src/libstore/realisation.hh
@@ -93,4 +93,14 @@ struct RealisedPath {
     GENERATE_CMP(RealisedPath, me->raw);
 };
 
+class MissingRealisation : public Error
+{
+public:
+    MissingRealisation(DrvOutput & outputId)
+        : Error( "cannot operate on an output of the "
+                "unbuilt derivation '%s'",
+                outputId.to_string())
+    {}
+};
+
 }
diff --git a/src/libstore/remote-store.cc b/src/libstore/remote-store.cc
index 48cf731a89e8..ccf7d7e8b18a 100644
--- a/src/libstore/remote-store.cc
+++ b/src/libstore/remote-store.cc
@@ -879,10 +879,7 @@ std::vector<BuildResult> RemoteStore::buildPathsWithResults(
                                 auto realisation =
                                     queryRealisation(outputId);
                                 if (!realisation)
-                                    throw Error(
-                                        "cannot operate on an output of unbuilt "
-                                        "content-addressed derivation '%s'",
-                                        outputId.to_string());
+                                    throw MissingRealisation(outputId);
                                 res.builtOutputs.emplace(realisation->id, *realisation);
                             } else {
                                 // If ca-derivations isn't enabled, assume that
diff --git a/src/nix/why-depends.cc b/src/nix/why-depends.cc
index 6512aee0376c..9abe634ec1b1 100644
--- a/src/nix/why-depends.cc
+++ b/src/nix/why-depends.cc
@@ -95,19 +95,27 @@ struct CmdWhyDepends : SourceExprCommand
          * to build.
          */
         auto dependency = parseInstallable(store, _dependency);
-        auto dependencyPath = Installable::toStorePath(getEvalStore(), store, Realise::Derivation, operateOn, dependency);
-        auto dependencyPathHash = dependencyPath.hashPart();
+        auto optDependencyPath = [&]() -> std::optional<StorePath> {
+            try {
+                return {Installable::toStorePath(getEvalStore(), store, Realise::Derivation, operateOn, dependency)};
+            } catch (MissingRealisation &) {
+                return std::nullopt;
+            }
+        }();
 
         StorePathSet closure;
         store->computeFSClosure({packagePath}, closure, false, false);
 
-        if (!closure.count(dependencyPath)) {
+        if (!optDependencyPath.has_value() || !closure.count(*optDependencyPath)) {
             printError("'%s' does not depend on '%s'",
-                store->printStorePath(packagePath),
-                store->printStorePath(dependencyPath));
+                package->what(),
+                dependency->what());
             return;
         }
 
+        auto dependencyPath = optDependencyPath.value();
+        auto dependencyPathHash = dependencyPath.hashPart();
+
         stopProgressBar(); // FIXME
 
         auto accessor = store->getFSAccessor();