diff --git a/src/frontend/variability.jl b/src/frontend/variability.jl
index 3fe625f27..a180d5d5c 100644
--- a/src/frontend/variability.jl
+++ b/src/frontend/variability.jl
@@ -14,6 +14,36 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-function flux_variability_analysis(model::A.AbstractFBCModel; optimizer, kwargs...)
-    #TODO
+"""
+$(TYPEDSIGNATURES)
+
+TODO
+"""
+function flux_variability_analysis(
+    model::A.AbstractFBCModel;
+    objective_bound,
+    optimizer,
+    settings,
+    workers = D.workers(),
+)
+    constraints = flux_balance_constraints(model)
+
+    objective = constraints.objective_value
+
+    objective_flux = optimized_constraints(
+        constraints;
+        objective = constraints.objective.value,
+        output = constraints.objective,
+        optimizer,
+        settings,
+    )
+
+    constraint_variability(
+        constraints *
+        :objective_bound^C.Constraint(objective, objective_bound(objective_flux)),
+        constraints.fluxes;
+        optimizer,
+        settings,
+        workers,
+    )
 end
diff --git a/src/solver.jl b/src/solver.jl
index 2d212668a..5c8b37f74 100644
--- a/src/solver.jl
+++ b/src/solver.jl
@@ -146,9 +146,9 @@ For a "nice" version for simpler finding of metabolic model optima, use
 [`flux_balance`](@ref).
 """
 function optimized_constraints(
-    constraints::C.ConstraintTreeElem;
+    constraints::C.ConstraintTree;
     settings = [],
-    output = constraints,
+    output::C.ConstraintTreeElem = constraints,
     kwargs...,
 )
     om = optimization_model(constraints; kwargs...)