diff --git a/src/Configuration.jl b/src/Configuration.jl
index 2b7eed6ae9..5cc95b0ada 100644
--- a/src/Configuration.jl
+++ b/src/Configuration.jl
@@ -156,7 +156,7 @@ These options are not intended to be changed during normal use.
 - `workspace_use_distributed_stdlib::Bool? = $WORKSPACE_USE_DISTRIBUTED_STDLIB_DEFAULT` Should we use the Distributed stdlib to run processes? Distributed will be replaced by Malt.jl, you can use this option to already get the old behaviour. `nothing` means: determine automatically (which is currently the same as `true`).
 - `lazy_workspace_creation::Bool = $LAZY_WORKSPACE_CREATION_DEFAULT`
 - `capture_stdout::Bool = $CAPTURE_STDOUT_DEFAULT`
-- `workspace_custom_startup_expr::Union{Nothing,Expr} = $WORKSPACE_CUSTOM_STARTUP_EXPR_DEFAULT` An expression to be evaluated in the workspace process before running notebook code.
+- `workspace_custom_startup_expr::Union{Nothing,String} = $WORKSPACE_CUSTOM_STARTUP_EXPR_DEFAULT` An expression to be evaluated in the workspace process before running notebook code.
 """
 @option mutable struct EvaluationOptions
     run_notebook_on_load::Bool = RUN_NOTEBOOK_ON_LOAD_DEFAULT
@@ -164,7 +164,17 @@ These options are not intended to be changed during normal use.
     workspace_use_distributed_stdlib::Union{Bool,Nothing} = WORKSPACE_USE_DISTRIBUTED_STDLIB_DEFAULT
     lazy_workspace_creation::Bool = LAZY_WORKSPACE_CREATION_DEFAULT
     capture_stdout::Bool = CAPTURE_STDOUT_DEFAULT
-    workspace_custom_startup_expr::Union{Nothing,Expr} = WORKSPACE_CUSTOM_STARTUP_EXPR_DEFAULT
+    workspace_custom_startup_expr::Union{Nothing,String} = WORKSPACE_CUSTOM_STARTUP_EXPR_DEFAULT
+end
+
+# TODO: deprecated, remove me in the next breaking release
+function Base.setproperty!(x::EvaluationOptions, property::Symbol, val)
+    if property === :workspace_custom_startup_expr && val isa Expr
+        @warn "Deprecated: workspace_custom_startup_expr should be a String, not an Expr."
+        setfield!(x, property, string(val))            
+    else
+        setfield!(x, property, val)
+    end
 end
 
 const COMPILE_DEFAULT = nothing
@@ -298,7 +308,7 @@ function from_flat_kwargs(;
         workspace_use_distributed_stdlib::Union{Bool,Nothing} = WORKSPACE_USE_DISTRIBUTED_STDLIB_DEFAULT,
         lazy_workspace_creation::Bool = LAZY_WORKSPACE_CREATION_DEFAULT,
         capture_stdout::Bool = CAPTURE_STDOUT_DEFAULT,
-        workspace_custom_startup_expr::Union{Nothing,Expr} = WORKSPACE_CUSTOM_STARTUP_EXPR_DEFAULT,
+        workspace_custom_startup_expr::Union{Nothing,String} = WORKSPACE_CUSTOM_STARTUP_EXPR_DEFAULT,
 
         compile::Union{Nothing,String} = COMPILE_DEFAULT,
         pkgimages::Union{Nothing,String} = PKGIMAGES_DEFAULT,
diff --git a/src/evaluation/WorkspaceManager.jl b/src/evaluation/WorkspaceManager.jl
index ba798bb114..cfd4d76939 100644
--- a/src/evaluation/WorkspaceManager.jl
+++ b/src/evaluation/WorkspaceManager.jl
@@ -73,7 +73,9 @@ function make_workspace((session, notebook)::SN; is_offline_renderer::Bool=false
     Status.report_business_planned!(init_status, Symbol(3))
     Status.report_business_planned!(init_status, Symbol(4))
 
-    Malt.remote_eval_wait(worker, session.options.evaluation.workspace_custom_startup_expr)
+    let s = session.options.evaluation.workspace_custom_startup_expr
+        s === nothing || Malt.remote_eval_wait(worker, Meta.parse(s))
+    end
 
     Malt.remote_eval_wait(worker, quote
         PlutoRunner.notebook_id[] = $(notebook.notebook_id)
diff --git a/test/Configuration.jl b/test/Configuration.jl
index 4d2d6c2f54..227e3d277e 100644
--- a/test/Configuration.jl
+++ b/test/Configuration.jl
@@ -132,6 +132,15 @@ end
         PlutoRunner.is_mime_enabled(m::MIME"application/vnd.pluto.tree+object") = false
     end
 
+    # backwards compat: setting the value to an Expr should still work
+    @test 🍭.options.evaluation.workspace_custom_startup_expr isa String
+    @test occursin("PlutoRunner.is_mime_enabled", 🍭.options.evaluation.workspace_custom_startup_expr)
+
+    # normally you set it to a String
+    🍭.options.evaluation.workspace_custom_startup_expr = """
+        PlutoRunner.is_mime_enabled(m::MIME"application/vnd.pluto.tree+object") = false
+    """
+
     nb = Pluto.Notebook([
         Pluto.Cell("x = [1, 2]")
         Pluto.Cell("struct Foo; x; end")