diff --git a/src/libstore/fetchers/fetchers.hh b/src/libstore/fetchers/fetchers.hh
index b59b328cc..1f3be8c2b 100644
--- a/src/libstore/fetchers/fetchers.hh
+++ b/src/libstore/fetchers/fetchers.hh
@@ -27,6 +27,8 @@ struct Input : std::enable_shared_from_this<Input>
     std::string type;
     std::optional<Hash> narHash;
 
+    virtual ~Input() { }
+
     virtual bool operator ==(const Input & other) const { return false; }
 
     virtual bool isDirect() const { return true; }
@@ -63,6 +65,8 @@ struct ParsedURL;
 
 struct InputScheme
 {
+    virtual ~InputScheme() { }
+
     virtual std::unique_ptr<Input> inputFromURL(const ParsedURL & url) = 0;
 };
 
diff --git a/src/libstore/fetchers/git.cc b/src/libstore/fetchers/git.cc
index bfa862cf5..16bbcd285 100644
--- a/src/libstore/fetchers/git.cc
+++ b/src/libstore/fetchers/git.cc
@@ -142,7 +142,7 @@ struct GitInput : Input
         return res;
     }
 
-    std::optional<Path> getSourcePath() const
+    std::optional<Path> getSourcePath() const override
     {
         if (url.scheme == "git+file" && !ref && !rev)
             return url.path;
@@ -172,7 +172,8 @@ struct GitInput : Input
                 return {std::move(*tree), input};
         }
 
-        auto [isLocal, actualUrl] = getActualUrl();
+        auto [isLocal, actualUrl_] = getActualUrl();
+        auto actualUrl = actualUrl_; // work around clang bug
 
         // If this is a local directory and no ref or revision is
         // given, then allow the use of an unclean working tree.
diff --git a/src/libstore/fetchers/mercurial.cc b/src/libstore/fetchers/mercurial.cc
index 64d5e84e1..304b2d967 100644
--- a/src/libstore/fetchers/mercurial.cc
+++ b/src/libstore/fetchers/mercurial.cc
@@ -84,7 +84,8 @@ struct MercurialInput : Input
 
         auto input = std::make_shared<MercurialInput>(*this);
 
-        auto [isLocal, actualUrl] = getActualUrl();
+        auto [isLocal, actualUrl_] = getActualUrl();
+        auto actualUrl = actualUrl_; // work around clang bug
 
         // FIXME: return lastModified.