diff --git a/CHANGELOG.md b/CHANGELOG.md
index 22e8acad8a..f37e4b45ac 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -47,6 +47,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fix scaling of transmission losses in write_transmission_losses.jl (#621)
 - Fix cost assignment to virtual storage charge/discharge - issue #604 (#608)
 - Fix modeling of hydro reservoir with long duration storage (#572).
+- Fix update of starting transmission capacity in multistage GenX
 
 ### Changed
 - Use add_to_expression! instead of the += and -= operators for memory performance improvements (#498).
diff --git a/src/multi_stage/dual_dynamic_programming.jl b/src/multi_stage/dual_dynamic_programming.jl
index 92f9791eb3..b3e2c23c14 100644
--- a/src/multi_stage/dual_dynamic_programming.jl
+++ b/src/multi_stage/dual_dynamic_programming.jl
@@ -362,11 +362,14 @@ function fix_initial_investments(EP_prev::Model, EP_cur::Model, start_cap_d::Dic
     # and the associated linking constraint name (c) as a value
     for (e, c) in start_cap_d
         for y in keys(EP_cur[c])
-	    if y[1] in ALL_CAP # extract resource integer index value from key
-                # Set the right hand side value of the linking initial capacity constraint in the current
-                # stage to the value of the available capacity variable solved for in the previous stages
-                set_normalized_rhs(EP_cur[c][y], value(EP_prev[e][y]))
-            end
+                # Set the right hand side value of the linking initial capacity constraint in the current stage to the value of the available capacity variable solved for in the previous stages
+                if c == :cExistingTransCap
+                    set_normalized_rhs(EP_cur[c][y], value(EP_prev[e][y]))
+                else
+	                if y[1] in ALL_CAP # extract resource integer index value from key
+                        set_normalized_rhs(EP_cur[c][y], value(EP_prev[e][y]))
+                    end
+                end
         end
     end
     return EP_cur