diff --git a/src/oemof/solph/flows/_simple_flow_block.py b/src/oemof/solph/flows/_simple_flow_block.py
index 469ec1311..7cf21bced 100644
--- a/src/oemof/solph/flows/_simple_flow_block.py
+++ b/src/oemof/solph/flows/_simple_flow_block.py
@@ -359,7 +359,7 @@ def _lifetime_age_output_rule(block):
                             m.flows[inp, out].lifetime - m.flows[inp, out].age
                             <= m.es.periods_years[p]
                         ):
-                            lhs = m.flow[inp, out, p, ts]
+                            lhs = m.flow[inp, out, ts]
                             rhs = 0
                             self.lifetime_age_output.add(
                                 (inp, out, p, ts), (lhs == rhs)
diff --git a/tests/lp_files/fixed_costs_sources.lp b/tests/lp_files/fixed_costs_sources.lp
index 8629b5295..20fdfeb81 100644
--- a/tests/lp_files/fixed_costs_sources.lp
+++ b/tests/lp_files/fixed_costs_sources.lp
@@ -2,90 +2,90 @@
 
 min 
 objective:
-+235.90542099192618 ONE_VAR_CONSTANT
-+25 flow(pv_forever_electricityBus_0_0)
-+25 flow(pv_forever_electricityBus_0_1)
-+24.509803921568626 flow(pv_forever_electricityBus_1_2)
-+24.509803921568626 flow(pv_forever_electricityBus_1_3)
-+24.029219530949632 flow(pv_forever_electricityBus_2_4)
-+24.029219530949632 flow(pv_forever_electricityBus_2_5)
-+25 flow(pv_with_lifetime_electricityBus_0_0)
-+25 flow(pv_with_lifetime_electricityBus_0_1)
-+24.509803921568626 flow(pv_with_lifetime_electricityBus_1_2)
-+24.509803921568626 flow(pv_with_lifetime_electricityBus_1_3)
-+24.029219530949632 flow(pv_with_lifetime_electricityBus_2_4)
-+24.029219530949632 flow(pv_with_lifetime_electricityBus_2_5)
-+25 flow(pv_with_lifetime_and_age_electricityBus_0_0)
-+25 flow(pv_with_lifetime_and_age_electricityBus_0_1)
-+24.509803921568626 flow(pv_with_lifetime_and_age_electricityBus_1_2)
-+24.509803921568626 flow(pv_with_lifetime_and_age_electricityBus_1_3)
-+24.029219530949632 flow(pv_with_lifetime_and_age_electricityBus_2_4)
-+24.029219530949632 flow(pv_with_lifetime_and_age_electricityBus_2_5)
++235.90542099192615 ONE_VAR_CONSTANT
++25 flow(pv_forever_electricityBus_0)
++25 flow(pv_forever_electricityBus_1)
++24.509803921568626 flow(pv_forever_electricityBus_2)
++24.509803921568626 flow(pv_forever_electricityBus_3)
++24.029219530949632 flow(pv_forever_electricityBus_4)
++24.029219530949632 flow(pv_forever_electricityBus_5)
++25 flow(pv_with_lifetime_electricityBus_0)
++25 flow(pv_with_lifetime_electricityBus_1)
++24.509803921568626 flow(pv_with_lifetime_electricityBus_2)
++24.509803921568626 flow(pv_with_lifetime_electricityBus_3)
++24.029219530949632 flow(pv_with_lifetime_electricityBus_4)
++24.029219530949632 flow(pv_with_lifetime_electricityBus_5)
++25 flow(pv_with_lifetime_and_age_electricityBus_0)
++25 flow(pv_with_lifetime_and_age_electricityBus_1)
++24.509803921568626 flow(pv_with_lifetime_and_age_electricityBus_2)
++24.509803921568626 flow(pv_with_lifetime_and_age_electricityBus_3)
++24.029219530949632 flow(pv_with_lifetime_and_age_electricityBus_4)
++24.029219530949632 flow(pv_with_lifetime_and_age_electricityBus_5)
 
 s.t.
 
-c_e_BusBlock_balance(electricityBus_0_0)_:
-+1 flow(pv_forever_electricityBus_0_0)
-+1 flow(pv_with_lifetime_electricityBus_0_0)
-+1 flow(pv_with_lifetime_and_age_electricityBus_0_0)
+c_e_BusBlock_balance(electricityBus_0)_:
++1 flow(pv_forever_electricityBus_0)
++1 flow(pv_with_lifetime_electricityBus_0)
++1 flow(pv_with_lifetime_and_age_electricityBus_0)
 = 0
 
-c_e_BusBlock_balance(electricityBus_0_1)_:
-+1 flow(pv_forever_electricityBus_0_1)
-+1 flow(pv_with_lifetime_electricityBus_0_1)
-+1 flow(pv_with_lifetime_and_age_electricityBus_0_1)
+c_e_BusBlock_balance(electricityBus_1)_:
++1 flow(pv_forever_electricityBus_1)
++1 flow(pv_with_lifetime_electricityBus_1)
++1 flow(pv_with_lifetime_and_age_electricityBus_1)
 = 0
 
-c_e_BusBlock_balance(electricityBus_1_2)_:
-+1 flow(pv_forever_electricityBus_1_2)
-+1 flow(pv_with_lifetime_electricityBus_1_2)
-+1 flow(pv_with_lifetime_and_age_electricityBus_1_2)
+c_e_BusBlock_balance(electricityBus_2)_:
++1 flow(pv_forever_electricityBus_2)
++1 flow(pv_with_lifetime_electricityBus_2)
++1 flow(pv_with_lifetime_and_age_electricityBus_2)
 = 0
 
-c_e_BusBlock_balance(electricityBus_1_3)_:
-+1 flow(pv_forever_electricityBus_1_3)
-+1 flow(pv_with_lifetime_electricityBus_1_3)
-+1 flow(pv_with_lifetime_and_age_electricityBus_1_3)
+c_e_BusBlock_balance(electricityBus_3)_:
++1 flow(pv_forever_electricityBus_3)
++1 flow(pv_with_lifetime_electricityBus_3)
++1 flow(pv_with_lifetime_and_age_electricityBus_3)
 = 0
 
-c_e_BusBlock_balance(electricityBus_2_4)_:
-+1 flow(pv_forever_electricityBus_2_4)
-+1 flow(pv_with_lifetime_electricityBus_2_4)
-+1 flow(pv_with_lifetime_and_age_electricityBus_2_4)
+c_e_BusBlock_balance(electricityBus_4)_:
++1 flow(pv_forever_electricityBus_4)
++1 flow(pv_with_lifetime_electricityBus_4)
++1 flow(pv_with_lifetime_and_age_electricityBus_4)
 = 0
 
-c_e_BusBlock_balance(electricityBus_2_5)_:
-+1 flow(pv_forever_electricityBus_2_5)
-+1 flow(pv_with_lifetime_electricityBus_2_5)
-+1 flow(pv_with_lifetime_and_age_electricityBus_2_5)
+c_e_BusBlock_balance(electricityBus_5)_:
++1 flow(pv_forever_electricityBus_5)
++1 flow(pv_with_lifetime_electricityBus_5)
++1 flow(pv_with_lifetime_and_age_electricityBus_5)
 = 0
 
 c_e_SimpleFlowBlock_lifetime_age_output(pv_with_lifetime_and_age_electricityBus_2_4)_:
-+1 flow(pv_with_lifetime_and_age_electricityBus_2_4)
++1 flow(pv_with_lifetime_and_age_electricityBus_4)
 = 0
 
 c_e_SimpleFlowBlock_lifetime_age_output(pv_with_lifetime_and_age_electricityBus_2_5)_:
-+1 flow(pv_with_lifetime_and_age_electricityBus_2_5)
++1 flow(pv_with_lifetime_and_age_electricityBus_5)
 = 0
 
 bounds
    1 <= ONE_VAR_CONSTANT <= 1
-   0 <= flow(pv_forever_electricityBus_0_0) <= 8.0
-   0 <= flow(pv_forever_electricityBus_0_1) <= 8.0
-   0 <= flow(pv_forever_electricityBus_1_2) <= 8.0
-   0 <= flow(pv_forever_electricityBus_1_3) <= 8.0
-   0 <= flow(pv_forever_electricityBus_2_4) <= 8.0
-   0 <= flow(pv_forever_electricityBus_2_5) <= 8.0
-   0 <= flow(pv_with_lifetime_electricityBus_0_0) <= 8.0
-   0 <= flow(pv_with_lifetime_electricityBus_0_1) <= 8.0
-   0 <= flow(pv_with_lifetime_electricityBus_1_2) <= 8.0
-   0 <= flow(pv_with_lifetime_electricityBus_1_3) <= 8.0
-   0 <= flow(pv_with_lifetime_electricityBus_2_4) <= 8.0
-   0 <= flow(pv_with_lifetime_electricityBus_2_5) <= 8.0
-   0 <= flow(pv_with_lifetime_and_age_electricityBus_0_0) <= 8.0
-   0 <= flow(pv_with_lifetime_and_age_electricityBus_0_1) <= 8.0
-   0 <= flow(pv_with_lifetime_and_age_electricityBus_1_2) <= 8.0
-   0 <= flow(pv_with_lifetime_and_age_electricityBus_1_3) <= 8.0
-   0 <= flow(pv_with_lifetime_and_age_electricityBus_2_4) <= 8.0
-   0 <= flow(pv_with_lifetime_and_age_electricityBus_2_5) <= 8.0
+   0 <= flow(pv_forever_electricityBus_0) <= 8.0
+   0 <= flow(pv_forever_electricityBus_1) <= 8.0
+   0 <= flow(pv_forever_electricityBus_2) <= 8.0
+   0 <= flow(pv_forever_electricityBus_3) <= 8.0
+   0 <= flow(pv_forever_electricityBus_4) <= 8.0
+   0 <= flow(pv_forever_electricityBus_5) <= 8.0
+   0 <= flow(pv_with_lifetime_electricityBus_0) <= 8.0
+   0 <= flow(pv_with_lifetime_electricityBus_1) <= 8.0
+   0 <= flow(pv_with_lifetime_electricityBus_2) <= 8.0
+   0 <= flow(pv_with_lifetime_electricityBus_3) <= 8.0
+   0 <= flow(pv_with_lifetime_electricityBus_4) <= 8.0
+   0 <= flow(pv_with_lifetime_electricityBus_5) <= 8.0
+   0 <= flow(pv_with_lifetime_and_age_electricityBus_0) <= 8.0
+   0 <= flow(pv_with_lifetime_and_age_electricityBus_1) <= 8.0
+   0 <= flow(pv_with_lifetime_and_age_electricityBus_2) <= 8.0
+   0 <= flow(pv_with_lifetime_and_age_electricityBus_3) <= 8.0
+   0 <= flow(pv_with_lifetime_and_age_electricityBus_4) <= 8.0
+   0 <= flow(pv_with_lifetime_and_age_electricityBus_5) <= 8.0
 end
diff --git a/tests/lp_files/flow_reaching_lifetime_initial_age.lp b/tests/lp_files/flow_reaching_lifetime_initial_age.lp
index 61f0a0a7a..e1f5c8da4 100644
--- a/tests/lp_files/flow_reaching_lifetime_initial_age.lp
+++ b/tests/lp_files/flow_reaching_lifetime_initial_age.lp
@@ -2,60 +2,60 @@
 
 min 
 objective:
-+25 flow(electricityBus_excess_0_0)
-+25 flow(electricityBus_excess_0_1)
-+24.509803921568626 flow(electricityBus_excess_1_2)
-+24.509803921568626 flow(electricityBus_excess_1_3)
-+24.029219530949632 flow(electricityBus_excess_2_4)
-+24.029219530949632 flow(electricityBus_excess_2_5)
++25 flow(electricityBus_excess_0)
++25 flow(electricityBus_excess_1)
++24.509803921568626 flow(electricityBus_excess_2)
++24.509803921568626 flow(electricityBus_excess_3)
++24.029219530949632 flow(electricityBus_excess_4)
++24.029219530949632 flow(electricityBus_excess_5)
 
 s.t.
 
-c_e_BusBlock_balance(electricityBus_0_0)_:
-+1 flow(electricityBus_excess_0_0)
+c_e_BusBlock_balance(electricityBus_0)_:
++1 flow(electricityBus_excess_0)
 = 0
 
-c_e_BusBlock_balance(electricityBus_0_1)_:
-+1 flow(electricityBus_excess_0_1)
+c_e_BusBlock_balance(electricityBus_1)_:
++1 flow(electricityBus_excess_1)
 = 0
 
-c_e_BusBlock_balance(electricityBus_1_2)_:
-+1 flow(electricityBus_excess_1_2)
+c_e_BusBlock_balance(electricityBus_2)_:
++1 flow(electricityBus_excess_2)
 = 0
 
-c_e_BusBlock_balance(electricityBus_1_3)_:
-+1 flow(electricityBus_excess_1_3)
+c_e_BusBlock_balance(electricityBus_3)_:
++1 flow(electricityBus_excess_3)
 = 0
 
-c_e_BusBlock_balance(electricityBus_2_4)_:
-+1 flow(electricityBus_excess_2_4)
+c_e_BusBlock_balance(electricityBus_4)_:
++1 flow(electricityBus_excess_4)
 = 0
 
-c_e_BusBlock_balance(electricityBus_2_5)_:
-+1 flow(electricityBus_excess_2_5)
+c_e_BusBlock_balance(electricityBus_5)_:
++1 flow(electricityBus_excess_5)
 = 0
 
 c_e_SimpleFlowBlock_lifetime_age_output(electricityBus_excess_1_2)_:
-+1 flow(electricityBus_excess_1_2)
++1 flow(electricityBus_excess_2)
 = 0
 
 c_e_SimpleFlowBlock_lifetime_age_output(electricityBus_excess_1_3)_:
-+1 flow(electricityBus_excess_1_3)
++1 flow(electricityBus_excess_3)
 = 0
 
 c_e_SimpleFlowBlock_lifetime_age_output(electricityBus_excess_2_4)_:
-+1 flow(electricityBus_excess_2_4)
++1 flow(electricityBus_excess_4)
 = 0
 
 c_e_SimpleFlowBlock_lifetime_age_output(electricityBus_excess_2_5)_:
-+1 flow(electricityBus_excess_2_5)
++1 flow(electricityBus_excess_5)
 = 0
 
 bounds
-   0 <= flow(electricityBus_excess_0_0) <= 8.0
-   0 <= flow(electricityBus_excess_0_1) <= 8.0
-   0 <= flow(electricityBus_excess_1_2) <= 8.0
-   0 <= flow(electricityBus_excess_1_3) <= 8.0
-   0 <= flow(electricityBus_excess_2_4) <= 8.0
-   0 <= flow(electricityBus_excess_2_5) <= 8.0
+   0 <= flow(electricityBus_excess_0) <= 8.0
+   0 <= flow(electricityBus_excess_1) <= 8.0
+   0 <= flow(electricityBus_excess_2) <= 8.0
+   0 <= flow(electricityBus_excess_3) <= 8.0
+   0 <= flow(electricityBus_excess_4) <= 8.0
+   0 <= flow(electricityBus_excess_5) <= 8.0
 end