diff --git a/src/systems/abstractsystem.jl b/src/systems/abstractsystem.jl
index d0474f1ba8..a350211386 100644
--- a/src/systems/abstractsystem.jl
+++ b/src/systems/abstractsystem.jl
@@ -201,6 +201,17 @@ function generate_custom_function(sys::AbstractSystem, exprs, dvs = unknowns(sys
     end
 end
 
+function wrap_assignments(isscalar, assignments; let_block = false)
+    function wrapper(expr)
+        Func(expr.args, [], Let(assignments, expr.body, let_block))
+    end
+    if isscalar
+        wrapper
+    else
+        wrapper, wrapper
+    end
+end
+
 function wrap_array_vars(sys::AbstractSystem, exprs; dvs = unknowns(sys))
     isscalar = !(exprs isa AbstractArray)
     array_vars = Dict{Any, AbstractArray{Int}}()
@@ -505,7 +516,7 @@ function SymbolicIndexingInterface.parameter_observed(sys::AbstractSystem, sym)
             ts_idx = nothing
         end
         rawobs = build_explicit_observed_function(
-                sys, sym; param_only = true, return_inplace = true)
+            sys, sym; param_only = true, return_inplace = true)
         if rawobs isa Tuple
             obsfn = let oop = rawobs[1], iip = rawobs[2]
                 f1(p::MTKParameters, t) = oop(p..., t)
diff --git a/src/systems/diffeqs/odesystem.jl b/src/systems/diffeqs/odesystem.jl
index 12e2ff16b2..b6ed52e49d 100644
--- a/src/systems/diffeqs/odesystem.jl
+++ b/src/systems/diffeqs/odesystem.jl
@@ -487,17 +487,23 @@ function build_explicit_observed_function(sys, ts;
     if inputs === nothing
         args = param_only ? [ps..., ivs...] : [dvs, ps..., ivs...]
     else
-        ipts = DestructuredArgs(inputs, inbounds = !checkbounds)
+        ipts = DestructuredArgs(unwrap.(inputs), inbounds = !checkbounds)
         args = param_only ? [ipts, ps..., ivs...] : [dvs, ipts, ps..., ivs...]
     end
     pre = get_postprocess_fbody(sys)
-    res = build_function(isscalar ? ts[1] : ts, args...; get_postprocess_fbody = pre, wrap_code = wrap_array_vars(sys, isscalar ? ts[1] : ts; dvs = param_only ? [] : unknowns(sys)), expression = Val{expression})
+    res = build_function(isscalar ? ts[1] : ts,
+        args...;
+        postprocess_fbody = pre,
+        wrap_code = wrap_array_vars(
+            sys, isscalar ? ts[1] : ts; dvs = param_only ? [] : unknowns(sys)) .∘
+                    wrap_assignments(isscalar, obsexprs),
+        expression = Val{expression})
     if isscalar || return_inplace
         return res
     else
         return res[1]
     end
-        
+
     ex = Func(args, [],
              pre(Let(obsexprs,
                  isscalar ? ts[1] : MakeArray(ts, output_type),