diff --git a/systems/provided/dynamic_small_system_optimise/data_for_optimisation.py b/systems/provided/dynamic_small_system_optimise/data_for_optimisation.py
index 156e0ac560..be561cdf40 100644
--- a/systems/provided/dynamic_small_system_optimise/data_for_optimisation.py
+++ b/systems/provided/dynamic_small_system_optimise/data_for_optimisation.py
@@ -15,6 +15,7 @@ def __init__(self, obj_instance: "objectiveFunctionForGreedy"):
         self.weights_optimal = obj_instance.weights_optimal
         self.per_contract_value = obj_instance.per_contract_value
         self.costs = obj_instance.costs
+        self.long_only = obj_instance.long_only
 
         if obj_instance.constraints is arg_not_supplied:
             reduce_only_keys = no_trade_keys = arg_not_supplied
diff --git a/systems/provided/dynamic_small_system_optimise/optimisation.py b/systems/provided/dynamic_small_system_optimise/optimisation.py
index 6ea008e32a..ba32e217fb 100644
--- a/systems/provided/dynamic_small_system_optimise/optimisation.py
+++ b/systems/provided/dynamic_small_system_optimise/optimisation.py
@@ -39,6 +39,7 @@ def __init__(
         previous_positions: portfolioWeights = arg_not_supplied,
         constraints: constraintsForDynamicOpt = arg_not_supplied,
         maximum_positions: portfolioWeights = arg_not_supplied,
+        long_only: list = arg_not_supplied,
         log: pst_logger = get_logger("objectiveFunctionForGreedy"),
     ):
 
@@ -53,6 +54,7 @@ def __init__(
 
         self.weights_optimal = weights_optimal
         self.contracts_optimal = contracts_optimal
+        self.long_only = long_only
 
         if previous_positions is arg_not_supplied:
             weights_prior = arg_not_supplied
diff --git a/systems/provided/dynamic_small_system_optimise/set_up_constraints.py b/systems/provided/dynamic_small_system_optimise/set_up_constraints.py
index 25bba896bd..56a7bb218f 100644
--- a/systems/provided/dynamic_small_system_optimise/set_up_constraints.py
+++ b/systems/provided/dynamic_small_system_optimise/set_up_constraints.py
@@ -72,6 +72,10 @@ def get_data_and_calculate_for_code(
         no_trade = False
     else:
         no_trade = instrument_code in input_data.no_trade_keys
+    if input_data.long_only is arg_not_supplied:
+        long_only = False
+    else:
+        long_only = instrument_code in input_data.long_only
 
     max_position = input_data.maximum_position_weight_for_code(instrument_code)
     weight_prior = input_data.prior_weight_for_code(instrument_code)
@@ -83,6 +87,7 @@ def get_data_and_calculate_for_code(
         max_position=max_position,
         weight_prior=weight_prior,
         optimium_weight=optimium_weight,
+        long_only=long_only,
     )
 
     return min_max_and_direction_and_start_for_code
@@ -94,6 +99,7 @@ def calculations_for_code(
     max_position: float = arg_not_supplied,
     weight_prior: float = arg_not_supplied,
     optimium_weight: float = np.nan,
+    long_only: bool = False,
 ):
 
     minimum, maximum = calculate_minima_and_maxima(
@@ -101,6 +107,7 @@ def calculations_for_code(
         no_trade=no_trade,
         max_position=max_position,
         weight_prior=weight_prior,
+        long_only=long_only,
     )
 
     assert maximum >= minimum
@@ -118,6 +125,7 @@ def calculations_for_code(
 
 def calculate_minima_and_maxima(
     reduce_only: bool = False,
+    long_only: bool = False,
     no_trade: bool = False,
     max_position: float = arg_not_supplied,
     weight_prior: float = arg_not_supplied,
@@ -126,6 +134,9 @@ def calculate_minima_and_maxima(
     minimum = -A_VERY_LARGE_NUMBER
     maximum = A_VERY_LARGE_NUMBER
 
+    if long_only:
+        minimum = 0.0
+
     if no_trade:
         if weight_prior is not arg_not_supplied:
             return weight_prior, weight_prior
@@ -136,7 +147,7 @@ def calculate_minima_and_maxima(
                 minimum = 0.0
                 maximum = weight_prior
             elif weight_prior < 0:
-                minimum = weight_prior
+                minimum = max(minimum, weight_prior)
                 maximum = 0.0
 
             else: