diff --git a/net/speedtest/speedtest.go b/net/speedtest/speedtest.go
index 7ab0881cc..a462dbeec 100644
--- a/net/speedtest/speedtest.go
+++ b/net/speedtest/speedtest.go
@@ -24,7 +24,7 @@ const (
 // conduct the test.
 type config struct {
 	Version      int           `json:"version"`
-	TestDuration time.Duration `json:"time"`
+	TestDuration time.Duration `json:"time,format:nano"`
 	Direction    Direction     `json:"direction"`
 }
 
diff --git a/tailcfg/tailcfg.go b/tailcfg/tailcfg.go
index b2c1a402c..e9f97bdc4 100644
--- a/tailcfg/tailcfg.go
+++ b/tailcfg/tailcfg.go
@@ -2903,7 +2903,7 @@ type SSHAction struct {
 
 	// SessionDuration, if non-zero, is how long the session can stay open
 	// before being forcefully terminated.
-	SessionDuration time.Duration `json:"sessionDuration,omitempty"`
+	SessionDuration time.Duration `json:"sessionDuration,omitempty,format:nano"`
 
 	// AllowAgentForwarding, if true, allows accepted connections to forward
 	// the ssh agent if requested.