diff --git a/app/models/cart_validations.rb b/app/models/cart_validations.rb
index ec1af380d..acd1d5759 100644
--- a/app/models/cart_validations.rb
+++ b/app/models/cart_validations.rb
@@ -118,6 +118,7 @@ def check_max_ems
       valid = Reservation.number_for_date_range(source, start_date..due_date,
                                                 equipment_model_id: model.id,
                                                 overdue: false).max
+      valid ||= 0
       # count overdue reservations for this eq model
       overdue = source.count { |r| r.equipment_model == model && r.overdue }
 
@@ -153,6 +154,7 @@ def check_max_cat
       max = cat.maximum_per_user
       s = source.select { |r| r.equipment_model.category == cat }
       s = Reservation.number_for_date_range(s, start_date..due_date).max
+      s ||= 0
       o = overdue.count { |r| r.equipment_model.category == cat }
       next unless s + o + q > max
       errors << "Only #{max} #{cat.name.pluralize} can be reserved at a time."
diff --git a/app/models/equipment_model.rb b/app/models/equipment_model.rb
index 68f898397..8ad02a570 100644
--- a/app/models/equipment_model.rb
+++ b/app/models/equipment_model.rb
@@ -167,9 +167,11 @@ def document_attributes=(document_attributes)
   def num_busy(start_date, due_date, source)
     # get the number busy (not able to be reserved) in the source reservations
     # uses 0 queries
-    Reservation.number_for_date_range(source, start_date..due_date,
-                                      equipment_model_id: id,
-                                      overdue: false).max + overdue_count
+    max = Reservation.number_for_date_range(source, start_date..due_date,
+                                            equipment_model_id: id,
+                                            overdue: false).max
+    max ||= 0
+    max + overdue_count
   end
 
   def num_available(start_date, due_date, source = nil)