diff --git a/guppylang/prelude/builtins.py b/guppylang/prelude/builtins.py
index 486dda11..57130818 100644
--- a/guppylang/prelude/builtins.py
+++ b/guppylang/prelude/builtins.py
@@ -569,6 +569,11 @@ class SizedIter:
     Annotating an iterator with an incorrect size is undefined behaviour.
     """
 
+    def __class_getitem__(cls, item: Any) -> type:
+        # Dummy implementation to allow subscripting of the `SizedIter` type in
+        # positions that are evaluated by the Python interpreter
+        return cls
+
     @guppy.custom(NoopCompiler())
     def __new__(iterator: L @ owned) -> "SizedIter[L, n]":  # type: ignore[type-arg]
         """Casts an iterator into a `SizedIter`."""
diff --git a/tests/integration/test_range.py b/tests/integration/test_range.py
index 32d33a61..da9104c4 100644
--- a/tests/integration/test_range.py
+++ b/tests/integration/test_range.py
@@ -1,5 +1,5 @@
 from guppylang.decorator import guppy
-from guppylang.prelude.builtins import nat, range
+from guppylang.prelude.builtins import nat, range, SizedIter, Range
 from guppylang.module import GuppyModule
 from tests.util import compile_guppy
 
@@ -20,7 +20,27 @@ def negative() -> int:
             total += 100 + x
         return total
 
+    @guppy(module)
+    def non_static() -> int:
+        total = 0
+        n = 4
+        for x in range(n + 1):
+            total += x + 100  # Make the initial 0 obvious
+        return total
+
     compiled = module.compile()
     validate(compiled)
     run_int_fn(compiled, expected=510)
     run_int_fn(compiled, expected=0, fn_name="negative")
+    run_int_fn(compiled, expected=510, fn_name="non_static")
+
+
+def test_static_size(validate):
+    module = GuppyModule("test")
+
+    @guppy(module)
+    def negative() -> SizedIter[Range, 10]:
+        return range(10)
+
+    validate(module.compile())
+