diff --git a/src/NetscriptFunctions/Hacknet.ts b/src/NetscriptFunctions/Hacknet.ts
index bb93b87e4..cbe6a433a 100644
--- a/src/NetscriptFunctions/Hacknet.ts
+++ b/src/NetscriptFunctions/Hacknet.ts
@@ -201,7 +201,11 @@ export function NetscriptHacknet(): InternalAPI<IHacknet> {
       (_upgName, _upgTarget = "", _count = 1) => {
         const upgName = helpers.string(ctx, "upgName", _upgName);
         const upgTarget = helpers.string(ctx, "upgTarget", _upgTarget);
-        const count = helpers.number(ctx, "count", _count);
+        const count = Math.floor(helpers.number(ctx, "count", _count));
+        // TODO (3.0.0): use helpers.positiveInteger
+        if (!(count >= 0)) {
+          throw helpers.errorMessage(ctx, "count may not be negative");
+        }
         if (!hasHacknetServers()) {
           return false;
         }