diff --git a/src/libstore/binary-cache-store.cc b/src/libstore/binary-cache-store.cc
index b536c6c00..46c5aa21b 100644
--- a/src/libstore/binary-cache-store.cc
+++ b/src/libstore/binary-cache-store.cc
@@ -114,11 +114,6 @@ void BinaryCacheStore::init()
     }
 }
 
-void BinaryCacheStore::notImpl()
-{
-    throw Error("operation not implemented for binary cache stores");
-}
-
 std::shared_ptr<std::string> BinaryCacheStore::getFile(const std::string & path)
 {
     std::promise<std::shared_ptr<std::string>> promise;
diff --git a/src/libstore/binary-cache-store.hh b/src/libstore/binary-cache-store.hh
index 5c2d0acfd..87d4aa438 100644
--- a/src/libstore/binary-cache-store.hh
+++ b/src/libstore/binary-cache-store.hh
@@ -27,8 +27,6 @@ protected:
 
     BinaryCacheStore(const Params & params);
 
-    [[noreturn]] void notImpl();
-
 public:
 
     virtual bool fileExists(const std::string & path) = 0;
@@ -65,7 +63,7 @@ public:
     bool isValidPathUncached(const Path & path) override;
 
     PathSet queryAllValidPaths() override
-    { notImpl(); }
+    { unsupported(); }
 
     void queryPathInfoUncached(const Path & path,
         std::function<void(std::shared_ptr<ValidPathInfo>)> success,
@@ -73,16 +71,16 @@ public:
 
     void queryReferrers(const Path & path,
         PathSet & referrers) override
-    { notImpl(); }
+    { unsupported(); }
 
     PathSet queryDerivationOutputs(const Path & path) override
-    { notImpl(); }
+    { unsupported(); }
 
     StringSet queryDerivationOutputNames(const Path & path) override
-    { notImpl(); }
+    { unsupported(); }
 
     Path queryPathFromHashPart(const string & hashPart) override
-    { notImpl(); }
+    { unsupported(); }
 
     bool wantMassQuery() override { return wantMassQuery_; }
 
@@ -99,32 +97,29 @@ public:
 
     void narFromPath(const Path & path, Sink & sink) override;
 
-    void buildPaths(const PathSet & paths, BuildMode buildMode) override
-    { notImpl(); }
-
     BuildResult buildDerivation(const Path & drvPath, const BasicDerivation & drv,
         BuildMode buildMode) override
-    { notImpl(); }
+    { unsupported(); }
 
     void ensurePath(const Path & path) override
-    { notImpl(); }
+    { unsupported(); }
 
     void addTempRoot(const Path & path) override
-    { notImpl(); }
+    { unsupported(); }
 
     void addIndirectRoot(const Path & path) override
-    { notImpl(); }
+    { unsupported(); }
 
     Roots findRoots() override
-    { notImpl(); }
+    { unsupported(); }
 
     void collectGarbage(const GCOptions & options, GCResults & results) override
-    { notImpl(); }
+    { unsupported(); }
 
     ref<FSAccessor> getFSAccessor() override;
 
     void addSignatures(const Path & storePath, const StringSet & sigs) override
-    { notImpl(); }
+    { unsupported(); }
 
     std::shared_ptr<std::string> getBuildLog(const Path & path) override;
 
diff --git a/src/libstore/legacy-ssh-store.cc b/src/libstore/legacy-ssh-store.cc
index befc560bf..de0562aef 100644
--- a/src/libstore/legacy-ssh-store.cc
+++ b/src/libstore/legacy-ssh-store.cc
@@ -148,12 +148,6 @@ struct LegacySSHStore : public Store
         sink(*savedNAR.data);
     }
 
-    /* Unsupported methods. */
-    [[noreturn]] void unsupported()
-    {
-        throw Error("operation not supported on SSH stores");
-    }
-
     PathSet queryAllValidPaths() override { unsupported(); }
 
     void queryReferrers(const Path & path, PathSet & referrers) override
@@ -177,9 +171,6 @@ struct LegacySSHStore : public Store
         const PathSet & references, bool repair) override
     { unsupported(); }
 
-    void buildPaths(const PathSet & paths, BuildMode buildMode) override
-    { unsupported(); }
-
     BuildResult buildDerivation(const Path & drvPath, const BasicDerivation & drv,
         BuildMode buildMode) override
     { unsupported(); }
diff --git a/src/libstore/store-api.cc b/src/libstore/store-api.cc
index 835bbb90e..850ea211d 100644
--- a/src/libstore/store-api.cc
+++ b/src/libstore/store-api.cc
@@ -523,6 +523,17 @@ const Store::Stats & Store::getStats()
 }
 
 
+void Store::buildPaths(const PathSet & paths, BuildMode buildMode)
+{
+    for (auto & path : paths)
+        if (isDerivation(path))
+            unsupported();
+
+    if (queryValidPaths(paths).size() != paths.size())
+        unsupported();
+}
+
+
 void copyStorePath(ref<Store> srcStore, ref<Store> dstStore,
     const Path & storePath, bool repair, bool dontCheckSigs)
 {
diff --git a/src/libstore/store-api.hh b/src/libstore/store-api.hh
index 067309c9e..b763849ad 100644
--- a/src/libstore/store-api.hh
+++ b/src/libstore/store-api.hh
@@ -18,6 +18,12 @@
 namespace nix {
 
 
+MakeError(SubstError, Error)
+MakeError(BuildError, Error) /* denotes a permanent build failure */
+MakeError(InvalidPath, Error)
+MakeError(Unsupported, Error)
+
+
 struct BasicDerivation;
 struct Derivation;
 class FSAccessor;
@@ -414,7 +420,7 @@ public:
        output paths can be created by running the builder, after
        recursively building any sub-derivations. For inputs that are
        not derivations, substitute them. */
-    virtual void buildPaths(const PathSet & paths, BuildMode buildMode = bmNormal) = 0;
+    virtual void buildPaths(const PathSet & paths, BuildMode buildMode = bmNormal);
 
     /* Build a single non-materialized derivation (i.e. not from an
        on-disk .drv file). Note that ‘drvPath’ is only used for
@@ -584,6 +590,12 @@ protected:
 
     Stats stats;
 
+    /* Unsupported methods. */
+    [[noreturn]] void unsupported()
+    {
+        throw Unsupported("requested operation is not supported by store ‘%s’", getUri());
+    }
+
 };
 
 
@@ -720,10 +732,4 @@ ValidPathInfo decodeValidPathInfo(std::istream & str,
    for paths created by makeFixedOutputPath() / addToStore(). */
 std::string makeFixedOutputCA(bool recursive, const Hash & hash);
 
-
-MakeError(SubstError, Error)
-MakeError(BuildError, Error) /* denotes a permanent build failure */
-MakeError(InvalidPath, Error)
-
-
 }