diff --git a/tests/parser/test_call_graph_stability.py b/tests/parser/test_call_graph_stability.py
new file mode 100644
index 0000000000..6785169ba3
--- /dev/null
+++ b/tests/parser/test_call_graph_stability.py
@@ -0,0 +1,68 @@
+import random
+import string
+
+import hypothesis.strategies as st
+import pytest
+from hypothesis import given, settings
+
+import vyper.ast as vy_ast
+from vyper.compiler.phases import CompilerData
+
+
+# random names for functions
+@settings(max_examples=20, deadline=None)
+@given(
+    st.lists(
+        st.tuples(
+            st.sampled_from(["@pure", "@view", "@nonpayable", "@payable"]),
+            st.text(alphabet=string.ascii_lowercase, min_size=1),
+        ),
+        unique_by=lambda x: x[1],  # unique on function name
+        min_size=1,
+        max_size=10,
+    )
+)
+@pytest.mark.fuzzing
+def test_call_graph_stability_fuzz(funcs):
+    def generate_func_def(mutability, func_name, i):
+        return f"""
+@internal
+{mutability}
+def {func_name}() -> uint256:
+    return {i}
+        """
+
+    func_defs = "\n".join(generate_func_def(m, s, i) for i, (m, s) in enumerate(funcs))
+
+    for _ in range(10):
+        func_names = [f for (_, f) in funcs]
+        random.shuffle(func_names)
+
+        self_calls = "\n".join(f"  self.{f}()" for f in func_names)
+        code = f"""
+{func_defs}
+
+@external
+def foo():
+{self_calls}
+        """
+        t = CompilerData(code)
+
+        # check the .called_functions data structure on foo() directly
+        foo = t.vyper_module_folded.get_children(vy_ast.FunctionDef, filters={"name": "foo"})[0]
+        foo_t = foo._metadata["type"]
+        assert [f.name for f in foo_t.called_functions] == func_names
+
+        # now for sanity, ensure the order that the function definitions appear
+        # in the IR is the same as the order of the calls
+        sigs = t.function_signatures
+        del sigs["foo"]
+        ir = t.ir_runtime
+        ir_funcs = []
+        # search for function labels
+        for d in ir.args:  # currently: (seq ... (seq (label foo ...)) ...)
+            if d.value == "seq" and d.args[0].value == "label":
+                r = d.args[0].args[0].value
+                if isinstance(r, str) and r.startswith("internal"):
+                    ir_funcs.append(r)
+        assert ir_funcs == [f.internal_function_label for f in sigs.values()]
diff --git a/vyper/semantics/types/function.py b/vyper/semantics/types/function.py
index 99a1957fd7..75fa3a1214 100644
--- a/vyper/semantics/types/function.py
+++ b/vyper/semantics/types/function.py
@@ -1,7 +1,7 @@
 import re
 import warnings
 from collections import OrderedDict
-from typing import Any, Dict, List, Optional, Set, Tuple
+from typing import Any, Dict, List, Optional, Tuple
 
 from vyper import ast as vy_ast
 from vyper.ast.validation import validate_call_args
@@ -28,7 +28,7 @@
 from vyper.semantics.types.shortcuts import UINT256_T
 from vyper.semantics.types.subscriptable import TupleT
 from vyper.semantics.types.utils import type_from_abi, type_from_annotation
-from vyper.utils import keccak256
+from vyper.utils import OrderedSet, keccak256
 
 
 class ContractFunctionT(VyperType):
@@ -89,7 +89,7 @@ def __init__(
         self.nonreentrant = nonreentrant
 
         # a list of internal functions this function calls
-        self.called_functions: Set["ContractFunctionT"] = set()
+        self.called_functions = OrderedSet()
 
         # special kwargs that are allowed in call site
         self.call_site_kwargs = {
diff --git a/vyper/utils.py b/vyper/utils.py
index 37a3f13b3d..2440117d0c 100644
--- a/vyper/utils.py
+++ b/vyper/utils.py
@@ -11,6 +11,19 @@
 from vyper.exceptions import DecimalOverrideException, InvalidLiteral
 
 
+class OrderedSet(dict):
+    """
+    a minimal "ordered set" class. this is needed in some places
+    because, while dict guarantees you can recover insertion order
+    vanilla sets do not.
+    no attempt is made to fully implement the set API, will add
+    functionality as needed.
+    """
+
+    def add(self, item):
+        self[item] = None
+
+
 class DecimalContextOverride(decimal.Context):
     def __setattr__(self, name, value):
         if name == "prec":