diff --git a/src/tapedfunction.jl b/src/tapedfunction.jl
index 5c8a7f5c..656bff40 100644
--- a/src/tapedfunction.jl
+++ b/src/tapedfunction.jl
@@ -133,6 +133,15 @@ end
 struct NOOPInstruction <: AbstractInstruction end
 
 @inline result(t::TapedFunction) = t.binding_values[t.retval_binding_slot]
+@inline function _arg(tf::TapedFunction, i::Int; default=nothing)
+    length(tf.arg_binding_slots) < i && return default
+    tf.arg_binding_slots[i] > 0 && return tf.binding_values[tf.arg_binding_slots[i]]
+    return default
+end
+@inline function _arg!(tf::TapedFunction, i::Int, v)
+    length(tf.arg_binding_slots) >= i &&
+        tf.arg_binding_slots[i] > 0 && _update_var!(tf, tf.arg_binding_slots[i], v)
+end
 
 function (tf::TapedFunction)(args...; callback=nothing, continuation=false)
     if !continuation # reset counter and retval_binding_slot to run from the start
@@ -143,10 +152,10 @@ function (tf::TapedFunction)(args...; callback=nothing, continuation=false)
     # set args
     if tf.counter <= 1
         # The first slot in `binding_values` is assumed to be `tf.func`.
-        tf.arg_binding_slots[1] > 0 && _update_var!(tf, tf.arg_binding_slots[1], tf.func)
+        _arg!(tf, 1, tf.func)
         for i in 1:length(args) # the subsequent arg_binding_slots are arguments
             slot = i + 1
-            tf.arg_binding_slots[slot] > 0 && _update_var!(tf, tf.arg_binding_slots[slot], args[i])
+            _arg!(tf, slot, args[i])
         end
     end
 
@@ -314,7 +323,7 @@ function translate!(tape::RawTape, ir::Core.CodeInfo)
     for (k, v) in bcache
         isa(k, Core.SlotNumber) && (slots[k.id] = v)
     end
-    arg_binding_slots = fill(0, maximum(keys(slots)))
+    arg_binding_slots = fill(0, maximum(keys(slots); init=0))
     for (k, v) in slots
         arg_binding_slots[k] = v
     end
diff --git a/src/tapedtask.jl b/src/tapedtask.jl
index 0d22a6fe..f3ec4236 100644
--- a/src/tapedtask.jl
+++ b/src/tapedtask.jl
@@ -174,7 +174,7 @@ function Base.copy(t::TapedTask; args=())
             # the task is running, we find the real args from the copied binding_values
             map(1:length(t.args)) do i
                 s = i + 1
-                tf.arg_binding_slots[s] > 0 ? tf.binding_values[tf.arg_binding_slots[s]] : t.args[i]
+                _arg(tf, s; default=t.args[i])
             end
         else
             # the task is not started yet, but no args is given
diff --git a/test/tapedtask.jl b/test/tapedtask.jl
index 29ec751e..6256e6bf 100644
--- a/test/tapedtask.jl
+++ b/test/tapedtask.jl
@@ -199,5 +199,14 @@
             ttask3 = copy(ttask; args=(4,))
             @test consume(ttask3) == 5
         end
+
+        @testset "Issue-148, unused argument" begin
+            function f(x)
+                produce(1)
+            end
+
+            ttask = TapedTask(f, 2)
+            @test consume(ttask) == 1
+        end
     end
 end