diff --git a/ctl/server.go b/ctl/server.go
index c451b5c78..b43c8d907 100644
--- a/ctl/server.go
+++ b/ctl/server.go
@@ -67,7 +67,7 @@ func BuildServerFlags(cmd *cobra.Command, srv *server.Command) {
 	flags.StringVar(&srv.Config.Etcd.InitCluster, "etcd.initial-cluster", srv.Config.Etcd.InitCluster, "Initial cluster name1=apurl1,name2=apurl2")
 
 	// External DB
-	flags.StringVar(&srv.Config.ExternalDB, "externaldb", "", "external (postgres) database DSN to use for ExternalQuery calls")
+	flags.StringVar(&srv.Config.ExternalDBDSN, "external-db-dsn", "", "external (postgres) database DSN to use for ExternalLookup calls")
 
 	// AntiEntropy
 	flags.DurationVar((*time.Duration)(&srv.Config.AntiEntropy.Interval), "anti-entropy.interval", (time.Duration)(srv.Config.AntiEntropy.Interval), "Interval at which to run anti-entropy routine.")
diff --git a/executor.go b/executor.go
index 4ae6044fc..c6252c7ba 100644
--- a/executor.go
+++ b/executor.go
@@ -4042,10 +4042,11 @@ func (e *executor) executeExternalLookup(ctx context.Context, qcx *Qcx, index st
 	if err != nil {
 		return ExtractedTable{}, errors.Wrap(err, "translating query result")
 	}
-	argRow := qr[0].(*Row)
+	argRow, ok := qr[0].(*Row)
+	if !ok {
+		return ExtractedTable{}, errors.Errorf("argument call result is a %T but expected a row", qr[0])
+	}
 	if !argRow.Any() {
-		// If we attempt to substitute in an empty slice, the substitution will fail.
-		// Do not attempt to execute the query.
 		return ExtractedTable{}, nil
 	}
 
diff --git a/holder.go b/holder.go
index fa9efe254..3f960433f 100644
--- a/holder.go
+++ b/holder.go
@@ -243,7 +243,7 @@ type HolderConfig struct {
 	RBFConfig           *rbfcfg.Config
 	AntiEntropyInterval time.Duration
 
-	ExternalDB string
+	ExternalDBDSN string
 }
 
 func DefaultHolderConfig() *HolderConfig {
@@ -733,10 +733,10 @@ func (h *Holder) Open() error {
 
 	h.txf.blueGreenOnIfRunningBlueGreen()
 
-	if h.cfg.ExternalDB != "" {
+	if h.cfg.ExternalDBDSN != "" {
 		h.Logger.Printf("connecting to external DB")
 
-		db, err := sql.Open("postgres", h.cfg.ExternalDB)
+		db, err := sql.Open("postgres", h.cfg.ExternalDBDSN)
 		if err != nil {
 			return errors.Wrap(err, "connecting to external database")
 		}
diff --git a/server.go b/server.go
index 6bbfa2ba4..38a77dd39 100644
--- a/server.go
+++ b/server.go
@@ -403,7 +403,7 @@ func OptServerDisCo(disCo disco.DisCo,
 // OptServerExternalDB configures a connection to an external postgres database.
 func OptServerExternalDB(dsn string) ServerOption {
 	return func(s *Server) error {
-		s.holderConfig.ExternalDB = dsn
+		s.holderConfig.ExternalDBDSN = dsn
 		return nil
 	}
 }
diff --git a/server/config.go b/server/config.go
index 9081e197c..484a4b0f1 100644
--- a/server/config.go
+++ b/server/config.go
@@ -223,8 +223,8 @@ type Config struct {
 	// result combines the history from all nodes.
 	QueryHistoryLength int `toml:"query-history-length"`
 
-	// ExternalDB is an external database to connect to for `ExternalLookup` queries.
-	ExternalDB string `toml:"external-db"`
+	// ExternalDBDSN is an external database to connect to for `ExternalLookup` queries.
+	ExternalDBDSN string `toml:"external-db-dsn"`
 }
 
 // MustValidate checks that all ports in a Config are unique and not zero.
diff --git a/server/server.go b/server/server.go
index 4422858b0..556e7b6b6 100644
--- a/server/server.go
+++ b/server/server.go
@@ -429,8 +429,8 @@ func (m *Command) SetupServer() error {
 		discoOpt,
 	}
 
-	if m.Config.ExternalDB != "" {
-		serverOptions = append(serverOptions, pilosa.OptServerExternalDB(m.Config.ExternalDB))
+	if m.Config.ExternalDBDSN != "" {
+		serverOptions = append(serverOptions, pilosa.OptServerExternalDB(m.Config.ExternalDBDSN))
 	}
 
 	serverOptions = append(serverOptions, m.serverOptions...)