diff --git a/app/Services/Deployment/AllocationSelectionService.php b/app/Services/Deployment/AllocationSelectionService.php
index ae334edd2..e14b11a17 100644
--- a/app/Services/Deployment/AllocationSelectionService.php
+++ b/app/Services/Deployment/AllocationSelectionService.php
@@ -64,7 +64,7 @@ class AllocationSelectionService
             // Ranges are stored in the ports array as an array which can be
             // better processed in the repository.
             if (preg_match(AssignmentService::PORT_RANGE_REGEX, $port, $matches)) {
-                if (abs($matches[2] - $matches[1]) > AssignmentService::PORT_RANGE_LIMIT) {
+                if (abs(intval($matches[2]) - intval($matches[1])) > AssignmentService::PORT_RANGE_LIMIT) {
                     throw new DisplayException(trans('exceptions.allocations.too_many_ports'));
                 }