diff --git a/src/awkward/_connect/numba/arrayview.py b/src/awkward/_connect/numba/arrayview.py
index c09b470536..ec19c1c7d1 100644
--- a/src/awkward/_connect/numba/arrayview.py
+++ b/src/awkward/_connect/numba/arrayview.py
@@ -1068,6 +1068,7 @@ def lower_asarray(context, builder, sig, args):
     whichpos = ak._connect.numba.layout.posat(
         context, builder, viewproxy.pos, viewtype.type.ARRAY
     )
+
     arrayptr = ak._connect.numba.layout.getat(
         context, builder, viewproxy.arrayptrs, whichpos
     )
@@ -1075,11 +1076,16 @@ def lower_asarray(context, builder, sig, args):
     bitwidth = ak._connect.numba.layout.type_bitwidth(rettype.dtype)
     itemsize = context.get_constant(numba.intp, bitwidth // 8)
 
-    data = numba.core.cgutils.pointer_add(
-        builder,
+    data_pointer_type = context.get_value_type(numba.types.CPointer(rettype.dtype))
+
+    typed_arrayptr = builder.inttoptr(
         arrayptr,
-        builder.mul(viewproxy.start, itemsize),
-        context.get_value_type(numba.types.CPointer(rettype.dtype)),
+        data_pointer_type,
+    )
+
+    data = builder.gep(
+        typed_arrayptr,
+        [viewproxy.start],
     )
 
     shape = context.make_tuple(
diff --git a/src/awkward/_connect/numba/layout.py b/src/awkward/_connect/numba/layout.py
index ebf614a88f..2051c0f670 100644
--- a/src/awkward/_connect/numba/layout.py
+++ b/src/awkward/_connect/numba/layout.py
@@ -4,7 +4,6 @@
 
 import json
 
-import llvmlite.ir
 import numba
 from numba.core.errors import NumbaTypeError, NumbaValueError
 
@@ -58,25 +57,30 @@ def string_numba_lower(
     baseptr = ak._connect.numba.layout.getat(
         context, builder, viewproxy.arrayptrs, whichnextpos
     )
-    rawptr = builder.add(
-        baseptr,
-        ak._connect.numba.layout.castint(
-            context, builder, viewtype.type.indextype.dtype, numba.intp, start
-        ),
-    )
-    rawptr_cast = builder.inttoptr(
-        rawptr,
-        llvmlite.ir.PointerType(llvmlite.ir.IntType(numba.intp.bitwidth // 8)),
+    start_cast = ak._connect.numba.layout.castint(
+        context, builder, viewtype.type.indextype.dtype, numba.intp, start
     )
     strsize = builder.sub(stop, start)
     strsize_cast = ak._connect.numba.layout.castint(
         context, builder, viewtype.type.indextype.dtype, numba.intp, strsize
     )
+    # ``baseptr`` is stored in the Awkward lookup table as an integer
+    # address. Reconstruct a typed pointer explicitly before applying
+    # pointer arithmetic with GEP.
+    uint8_pointer_type = context.get_value_type(numba.types.CPointer(numba.types.uint8))
+    typed_baseptr = builder.inttoptr(
+        baseptr,
+        uint8_pointer_type,
+    )
+    rawptr = builder.gep(
+        typed_baseptr,
+        [start_cast],
+    )
 
     pyapi = context.get_python_api(builder)
     gil = pyapi.gil_ensure()
 
-    strptr = builder.bitcast(rawptr_cast, pyapi.cstring)
+    strptr = builder.bitcast(rawptr, pyapi.cstring)
 
     if viewtype.type.parameters["__array__"] == "string":
         kind = context.get_constant(numba.types.int32, pyapi.py_unicode_1byte_kind)
@@ -353,24 +357,33 @@ def posat(context, builder, pos, offset):
 
 
 def getat(context, builder, baseptr, offset, rettype=None):
-    ptrtype = None
-    if rettype is not None:
-        ptrtype = context.get_value_type(numba.types.CPointer(rettype))
-        bitwidth = type_bitwidth(rettype)
-    else:
-        bitwidth = numba.intp.bitwidth
-    byteoffset = builder.mul(offset, context.get_constant(numba.intp, bitwidth // 8))
-    out = builder.load(
-        numba.core.cgutils.pointer_add(builder, baseptr, byteoffset, ptrtype)
+    """
+    Load an element from an external buffer address.
+
+    Awkward's lookup table stores buffer pointers as integer addresses.
+    Convert the address explicitly to a typed pointer before using GEP.
+    """
+    element_type = numba.intp if rettype is None else rettype
+    pointer_type = context.get_value_type(numba.types.CPointer(element_type))
+    typed_baseptr = builder.inttoptr(
+        baseptr,
+        pointer_type,
     )
+
+    element_ptr = builder.gep(
+        typed_baseptr,
+        [offset],
+    )
+
+    out = builder.load(element_ptr)
+
     if rettype is not None and isinstance(rettype, numba.types.Boolean):
         return builder.icmp_signed(
             "!=",
             out,
             context.get_constant(numba.int8, 0),
         )
-    else:
-        return out
+    return out
 
 
 def regularize_atval(context, builder, viewproxy, attype, atval, wrapneg, checkbounds):
diff --git a/tests/test_4251_numba_intaddr_pointer_reconstruction.py b/tests/test_4251_numba_intaddr_pointer_reconstruction.py
new file mode 100644
index 0000000000..885858d39c
--- /dev/null
+++ b/tests/test_4251_numba_intaddr_pointer_reconstruction.py
@@ -0,0 +1,68 @@
+# BSD 3-Clause License; see https://github.com/scikit-hep/awkward/blob/main/LICENSE
+
+from __future__ import annotations
+
+import pytest
+
+import awkward as ak
+
+numba = pytest.importorskip("numba")
+
+ak.numba.register_and_check()
+
+
+@pytest.mark.parametrize(
+    "array",
+    [
+        ak.Array([True, False, True]),
+        ak.Array([1, 2, 3]),
+        ak.Array([1.5, 2.5, 3.5]),
+        ak.Array([[1, 2], [], [3]]),
+        ak.Array(["hello", "world"]),
+        ak.Array([b"hello", b"\x00\xff"]),
+    ],
+)
+def test_numba_getitem_after_pointer_conversion(array):
+    @numba.njit
+    def getitem(array, index):
+        return array[index]
+
+    for index, expected in enumerate(array.to_list()):
+        assert ak.to_list(getitem(array, index)) == expected
+
+
+def test_numba_ragged_string_membership():
+    array = ak.Array(
+        [
+            ["TRA", "TRB"],
+            [],
+            None,
+            ["TRG", "TRA"],
+        ]
+    )
+
+    @numba.njit
+    def isin(array, haystack, builder):
+        for row in array:
+            builder.begin_list()
+
+            if row is not None:
+                for value in row:
+                    builder.append(value in haystack)
+
+            builder.end_list()
+
+        return builder
+
+    result = isin(
+        array,
+        ("TRA", "TRB"),
+        ak.ArrayBuilder(),
+    ).snapshot()
+
+    assert result.to_list() == [
+        [True, True],
+        [],
+        [],
+        [False, True],
+    ]