diff --git a/nixos/modules/services/video/unifi-video.nix b/nixos/modules/services/video/unifi-video.nix
index 43208a9fe4cf..366a7111fde4 100644
--- a/nixos/modules/services/video/unifi-video.nix
+++ b/nixos/modules/services/video/unifi-video.nix
@@ -16,7 +16,7 @@ let
     -pidfile ${cfg.pidFile} \
     -procname unifi-video \
     -Djava.security.egd=file:/dev/./urandom \
-    -Xmx${cfg.maximumJavaHeapSize}M \
+    -Xmx${toString cfg.maximumJavaHeapSize}M \
     -Xss512K \
     -XX:+UseG1GC \
     -XX:+UseStringDeduplication \