diff --git a/fickling/fickle.py b/fickling/fickle.py
index c71b7f1..bfb7d2a 100644
--- a/fickling/fickle.py
+++ b/fickling/fickle.py
@@ -2066,6 +2066,24 @@ def run(self, interpreter: Interpreter):
         interpreter.stack.append(make_constant(False))
 
 
+class NextBuffer(Opcode):
+    name = "NEXT_BUFFER"
+
+    def run(self, interpreter: Interpreter):
+        # The buffer contents are out-of-band: they are not part of the pickle
+        # stream, so the analysis models them as an opaque value.
+        interpreter.stack.append(ast.Name("out_of_band_buffer", ast.Load()))
+
+
+class ReadOnlyBuffer(Opcode):
+    name = "READONLY_BUFFER"
+
+    def run(self, interpreter: Interpreter):
+        # Marks the buffer on the top of the stack read-only; the value itself
+        # is unchanged, so this is a no-op for the AST.
+        pass
+
+
 class Tuple(StackSliceOpcode):
     name = "TUPLE"
 
@@ -2386,6 +2404,22 @@ class BinBytes8(BinBytes):
     length_bytes = 8
 
 
+class ByteArray8(BinBytes8):
+    name = "BYTEARRAY8"
+    priority = BinBytes8.priority + 1
+
+    def encode_body(self) -> bytes:
+        return bytes(self.arg)
+
+    @classmethod
+    def validate(cls, obj):
+        if not isinstance(obj, bytearray):
+            raise ValueError(
+                f"{cls.__name__} must be instantiated with an object of type bytearray, not {obj!r}"
+            )
+        return super().validate(obj)
+
+
 class Long1(ConstantInt):
     name = "LONG1"
     num_bytes = 1
@@ -2418,6 +2452,20 @@ class Long(Int):
     priority = Int.priority + 1
 
 
+class Float(ConstantOpcode):
+    name = "FLOAT"
+    priority = Long.priority + 1
+
+    def encode_body(self) -> bytes:
+        return f"{self.arg}\n".encode()
+
+    @classmethod
+    def validate(cls, obj):
+        if not isinstance(obj, float):
+            raise ValueError(f"{cls.__name__} expects a float, but received {obj!r}")
+        return obj
+
+
 class Dict(Opcode):
     name = "DICT"
 
diff --git a/test/test_pickle.py b/test/test_pickle.py
index 9318244..1e429aa 100644
--- a/test/test_pickle.py
+++ b/test/test_pickle.py
@@ -1,3 +1,5 @@
+import ast
+import io
 import pickle
 from ast import unparse
 from contextlib import redirect_stdout
@@ -491,3 +493,37 @@ def test_ext_with_function(self):
             self.assertEqual(result, real_result)
         finally:
             copyreg.remove_extension("os.path", "join", 200)
+
+
+class TestUnimplementedOpcodeRegression(TestCase):
+    """Regression tests: these four standard opcodes previously raised
+    NotImplementedError at load time, crashing the security analysis on benign
+    pickles (a float in a legacy protocol-0 file; a bytearray or out-of-band
+    buffer in a protocol-5 file)."""
+
+    def test_float_proto0(self):
+        pickled = Pickled.load(io.BytesIO(dumps(1.5, protocol=0)))
+        self.assertEqual(1.5, get_result(pickled))
+
+    def test_bytearray8_proto5(self):
+        pickled = Pickled.load(io.BytesIO(dumps(bytearray(b"hi"), protocol=5)))
+        constants = [n.value for n in ast.walk(pickled.ast) if isinstance(n, ast.Constant)]
+        self.assertIn(bytearray(b"hi"), constants)
+
+    def test_next_buffer_and_readonly_buffer_do_not_crash(self):
+        # PROTO 5, NEXT_BUFFER, READONLY_BUFFER, STOP: an out-of-band buffer's
+        # opcode sequence (the buffer contents live outside the stream).
+        stream = b"\x80\x05\x97\x98."
+        pickled = Pickled.load(io.BytesIO(stream))
+        names = [n.id for n in ast.walk(pickled.ast) if isinstance(n, ast.Name)]
+        self.assertIn("out_of_band_buffer", names)
+        check_safety(pickled)
+
+    def test_load_never_raises_notimplementederror(self):
+        for stream in (
+            dumps(1.5, protocol=0),
+            dumps(bytearray(b"hi"), protocol=5),
+            b"\x80\x05\x97\x98.",
+        ):
+            with self.subTest(stream=stream):
+                Pickled.load(io.BytesIO(stream))