diff --git a/cmd/tsconnect/wasm/wasm_js.go b/cmd/tsconnect/wasm/wasm_js.go
index 8bc64e18e..d37921211 100644
--- a/cmd/tsconnect/wasm/wasm_js.go
+++ b/cmd/tsconnect/wasm/wasm_js.go
@@ -1278,7 +1278,7 @@ func (i *jsIPN) ping(ip string, pingType string, size int) js.Value {
 		case tailcfg.PingDisco, tailcfg.PingTSMP, tailcfg.PingICMP, tailcfg.PingPeerAPI:
 			// valid
 		default:
-			return nil, fmt.Errorf("ping: unknown type %q, must be one of: disco, TSMP, icmp, peerapi", pingType)
+			return nil, fmt.Errorf("ping: unknown type %q, must be one of: disco, TSMP, ICMP, peerapi", pingType)
 		}
 		ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
 		defer cancel()