diff --git a/src/parameter_indexing.jl b/src/parameter_indexing.jl
index b441070..f01f651 100644
--- a/src/parameter_indexing.jl
+++ b/src/parameter_indexing.jl
@@ -622,7 +622,7 @@ for (t1, t2) in [
             end
             return getter
         else
-            pofn = supports_tuple ? parameter_observed(sys, p) :
+            pofn = supports_tuple ? parameter_observed(sys, _p) :
                    parameter_observed(sys, p_arr)
             if pofn === nothing
                 return MultipleParametersGetter.(getters)
diff --git a/test/parameter_indexing_test.jl b/test/parameter_indexing_test.jl
index b3d6e73..2c5ebd1 100644
--- a/test/parameter_indexing_test.jl
+++ b/test/parameter_indexing_test.jl
@@ -115,7 +115,8 @@ for sys in [
             ((1, :c), Tuple(p[[1, 3]]), true),
             (:(a + b + t), p[1] + p[2] + fi.t, true),
             ([:(a + b + t), :c], [p[1] + p[2] + fi.t, p[3]], true),
-            ((:(a + b + t), :c), (p[1] + p[2] + fi.t, p[3]), true)
+            ((:(a + b + t), :c), (p[1] + p[2] + fi.t, p[3]), true),
+            ((; a = (; b = :(a + b))), (; a = (; b = p[1] + p[2])), true),
         ]
             get = getp(sys, sym)
             if check_inference