diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index 2fd160dd4..a612deb3e 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -1585,20 +1585,6 @@ void LocalStore::addSignatures(const StorePath & storePath, const StringSet & si
 }
 
 
-void LocalStore::signPathInfo(ValidPathInfo & info)
-{
-    // FIXME: keep secret keys in memory.
-
-    auto secretKeyFiles = settings.secretKeyFiles;
-
-    for (auto & secretKeyFile : secretKeyFiles.get()) {
-        SecretKey secretKey(readFile(secretKeyFile));
-        LocalSigner signer(std::move(secretKey));
-        info.sign(*this, signer);
-    }
-}
-
-
 std::optional<std::pair<int64_t, Realisation>> LocalStore::queryRealisationCore_(
         LocalStore::State & state,
         const DrvOutput & id)
diff --git a/src/libstore/local-store.hh b/src/libstore/local-store.hh
index 07d9cec0a..680318d43 100644
--- a/src/libstore/local-store.hh
+++ b/src/libstore/local-store.hh
@@ -396,12 +396,6 @@ private:
     bool isValidPath_(State & state, const StorePath & path);
     void queryReferrers(State & state, const StorePath & path, StorePathSet & referrers);
 
-    /**
-     * Add signatures to a ValidPathInfo or Realisation using the secret keys
-     * specified by the ‘secret-key-files’ option.
-     */
-    void signPathInfo(ValidPathInfo & info);
-
     void addBuildLog(const StorePath & drvPath, std::string_view log) override;
 
     friend struct LocalDerivationGoal;
diff --git a/src/libstore/store-api.cc b/src/libstore/store-api.cc
index e99e96aac..172c82324 100644
--- a/src/libstore/store-api.cc
+++ b/src/libstore/store-api.cc
@@ -1274,6 +1274,21 @@ Derivation Store::readDerivation(const StorePath & drvPath)
 Derivation Store::readInvalidDerivation(const StorePath & drvPath)
 { return readDerivationCommon(*this, drvPath, false); }
 
+
+void Store::signPathInfo(ValidPathInfo & info)
+{
+    // FIXME: keep secret keys in memory.
+
+    auto secretKeyFiles = settings.secretKeyFiles;
+
+    for (auto & secretKeyFile : secretKeyFiles.get()) {
+        SecretKey secretKey(readFile(secretKeyFile));
+        LocalSigner signer(std::move(secretKey));
+        info.sign(*this, signer);
+    }
+}
+
+
 void Store::signRealisation(Realisation & realisation)
 {
     // FIXME: keep secret keys in memory.
diff --git a/src/libstore/store-api.hh b/src/libstore/store-api.hh
index 83ca8344b..1ae4ac064 100644
--- a/src/libstore/store-api.hh
+++ b/src/libstore/store-api.hh
@@ -622,6 +622,12 @@ public:
     virtual void addSignatures(const StorePath & storePath, const StringSet & sigs)
     { unsupported("addSignatures"); }
 
+    /**
+     * Add signatures to a ValidPathInfo or Realisation using the secret keys
+     * specified by the ‘secret-key-files’ option.
+     */
+    void signPathInfo(ValidPathInfo & info);
+
     void signRealisation(Realisation &);
 
     /* Utility functions. */