diff --git a/src/batched_interface.jl b/src/batched_interface.jl
index d6e8dbb..3be5c71 100644
--- a/src/batched_interface.jl
+++ b/src/batched_interface.jl
@@ -189,28 +189,73 @@ function setu(bi::BatchedInterface)
     numprobs = length(bi.system_to_symbol_subset)
     probnames = [Symbol(:prob, i) for i in 1:numprobs]
 
-    fnbody = quote end
-    for (sys_idx, subset) in enumerate(bi.system_to_symbol_subset)
-        probname = probnames[sys_idx]
-        for (idx_in_subset, idx_in_union) in enumerate(subset)
-            idx = bi.system_to_symbol_indexes[sys_idx][idx_in_subset]
-            isstate = bi.system_to_isstate[sys_idx][idx_in_subset]
-            setter = isstate ? set_state! : set_parameter!
-            push!(fnbody.args, :($setter($probname, vals[$idx_in_union], $idx)))
+    full_update_fnexpr = let fnbody = quote end
+        for (sys_idx, subset) in enumerate(bi.system_to_symbol_subset)
+            probname = probnames[sys_idx]
+            for (idx_in_subset, idx_in_union) in enumerate(subset)
+                idx = bi.system_to_symbol_indexes[sys_idx][idx_in_subset]
+                isstate = bi.system_to_isstate[sys_idx][idx_in_subset]
+                setter = isstate ? set_state! : set_parameter!
+                push!(fnbody.args, :($setter($probname, vals[$idx_in_union], $idx)))
+            end
+            # also run hook
+            if !all(bi.system_to_isstate[sys_idx])
+                paramidxs = [bi.system_to_symbol_indexes[sys_idx][idx_in_subset]
+                             for idx_in_subset in 1:length(subset)
+                             if !bi.system_to_isstate[sys_idx][idx_in_subset]]
+                push!(fnbody.args, :($finalize_parameters_hook!($probname, $paramidxs)))
+            end
         end
-        # also run hook
-        if !all(bi.system_to_isstate[sys_idx])
-            paramidxs = [bi.system_to_symbol_indexes[sys_idx][idx_in_subset]
-                         for idx_in_subset in 1:length(subset)
-                         if !bi.system_to_isstate[sys_idx][idx_in_subset]]
-            push!(fnbody.args, :($finalize_parameters_hook!($probname, $paramidxs)))
+        push!(fnbody.args, :(return vals))
+        Expr(
+            :function,
+            Expr(:tuple, probnames..., :vals),
+            fnbody
+        )
+    end
+
+    partial_update_fnexpr = let fnbody = quote end
+        curfnbody = fnbody
+        for (sys_idx, subset) in enumerate(bi.system_to_symbol_subset)
+            newcurfnbody = if sys_idx == 1
+                Expr(:if, :(idx == $sys_idx))
+            else
+                Expr(:elseif, :(idx == $sys_idx))
+            end
+            push!(curfnbody.args, newcurfnbody)
+            curfnbody = newcurfnbody
+
+            ifbody = quote end
+            push!(curfnbody.args, ifbody)
+
+            probname = :prob
+            for (idx_in_subset, idx_in_union) in enumerate(subset)
+                idx = bi.system_to_symbol_indexes[sys_idx][idx_in_subset]
+                isstate = bi.system_to_isstate[sys_idx][idx_in_subset]
+                setter = isstate ? set_state! : set_parameter!
+                push!(ifbody.args, :($setter($probname, vals[$idx_in_union], $idx)))
+            end
+            # also run hook
+            if !all(bi.system_to_isstate[sys_idx])
+                paramidxs = [bi.system_to_symbol_indexes[sys_idx][idx_in_subset]
+                             for idx_in_subset in 1:length(subset)
+                             if !bi.system_to_isstate[sys_idx][idx_in_subset]]
+                push!(ifbody.args, :($finalize_parameters_hook!($probname, $paramidxs)))
+            end
         end
+        push!(curfnbody.args, :(error("Invalid problem index $idx")))
+        push!(fnbody.args, :(return nothing))
+        Expr(
+            :function,
+            Expr(:tuple, :prob, :idx, :vals),
+            fnbody
+        )
+    end
+    return let full_update = @RuntimeGeneratedFunction(full_update_fnexpr),
+        partial_update = @RuntimeGeneratedFunction(partial_update_fnexpr)
+
+        setter!(args...) = full_update(args...)
+        setter!(prob, idx::Int, vals::AbstractVector) = partial_update(prob, idx, vals)
+        setter!
     end
-    push!(fnbody.args, :(return vals))
-    fnexpr = Expr(
-        :function,
-        Expr(:tuple, probnames..., :vals),
-        fnbody
-    )
-    return @RuntimeGeneratedFunction(fnexpr)
 end
diff --git a/test/batched_interface_test.jl b/test/batched_interface_test.jl
index 9cf5cd7..3e622cd 100644
--- a/test/batched_interface_test.jl
+++ b/test/batched_interface_test.jl
@@ -47,3 +47,10 @@ setter!(probs..., buf)
 @test state_values(probs[3]) == [500.0, 100.0, 9.0]
 # Similarly for :f
 @test parameter_values(probs[3]) == [70.0, 80.0, 0.9]
+
+buf ./= 100
+setter!(probs[1], 1, buf)
+@test state_values(probs[1]) == [1.0, 2.0, 3.0]
+@test parameter_values(probs[1]) == [0.1, 0.2, 0.3]
+
+@test_throws ErrorException setter!(probs[1], 4, buf)