diff --git a/src/libstore/remote-store.cc b/src/libstore/remote-store.cc
index 430d0ecf1..1edf3662e 100644
--- a/src/libstore/remote-store.cc
+++ b/src/libstore/remote-store.cc
@@ -243,7 +243,18 @@ std::shared_ptr<ValidPathInfo> RemoteStore::queryPathInfoUncached(const Path & p
 {
     auto conn(connections->get());
     conn->to << wopQueryPathInfo << path;
-    conn->processStderr();
+    try {
+        conn->processStderr();
+    } catch (Error & e) {
+        // Ugly backwards compatibility hack.
+        if (e.msg().find("is not valid") != std::string::npos)
+            throw InvalidPath(e.what());
+        throw;
+    }
+    if (GET_PROTOCOL_MINOR(conn->daemonVersion) >= 17) {
+        bool valid = readInt(conn->from) != 0;
+        if (!valid) throw InvalidPath(format("path ‘%s’ is not valid") % path);
+    }
     auto info = std::make_shared<ValidPathInfo>();
     info->path = path;
     info->deriver = readString(conn->from);
diff --git a/src/libstore/worker-protocol.hh b/src/libstore/worker-protocol.hh
index d62244d18..d133328d1 100644
--- a/src/libstore/worker-protocol.hh
+++ b/src/libstore/worker-protocol.hh
@@ -6,7 +6,7 @@ namespace nix {
 #define WORKER_MAGIC_1 0x6e697863
 #define WORKER_MAGIC_2 0x6478696f
 
-#define PROTOCOL_VERSION 0x110
+#define PROTOCOL_VERSION 0x111
 #define GET_PROTOCOL_MAJOR(x) ((x) & 0xff00)
 #define GET_PROTOCOL_MINOR(x) ((x) & 0x00ff)
 
diff --git a/src/nix-daemon/nix-daemon.cc b/src/nix-daemon/nix-daemon.cc
index dfb5da4ad..efc67b6a8 100644
--- a/src/nix-daemon/nix-daemon.cc
+++ b/src/nix-daemon/nix-daemon.cc
@@ -495,15 +495,23 @@ static void performOp(ref<LocalStore> store, bool trusted, unsigned int clientVe
 
     case wopQueryPathInfo: {
         Path path = readStorePath(from);
+        std::shared_ptr<const ValidPathInfo> info;
         startWork();
-        auto info = store->queryPathInfo(path);
-        stopWork();
-        to << info->deriver << printHash(info->narHash) << info->references
-           << info->registrationTime << info->narSize;
-        if (GET_PROTOCOL_MINOR(clientVersion) >= 16) {
-            to << info->ultimate
-               << info->sigs;
+        try {
+            info = store->queryPathInfo(path);
+        } catch (InvalidPath &) {
+            if (GET_PROTOCOL_MINOR(clientVersion) < 17) throw;
         }
+        stopWork();
+        if (info) {
+            to << 1 << info->deriver << printHash(info->narHash) << info->references
+               << info->registrationTime << info->narSize;
+            if (GET_PROTOCOL_MINOR(clientVersion) >= 16) {
+                to << info->ultimate
+                   << info->sigs;
+            }
+        } else
+            to << 0;
         break;
     }