diff --git a/crosshair/diff_behavior.py b/crosshair/diff_behavior.py
index 934acd93..375f3f41 100644
--- a/crosshair/diff_behavior.py
+++ b/crosshair/diff_behavior.py
@@ -17,6 +17,7 @@
     StateSpaceContext,
     VerificationStatus,
 )
+from crosshair.test_util import flexible_equal
 from crosshair.tracers import (
     COMPOSITE_TRACER,
     CoverageResult,
@@ -227,7 +228,7 @@ def run_iteration(
         result1 = describe_behavior(fn1, args1)
         result2 = describe_behavior(fn2, args2)
         space.detach_path()
-        if result1 == result2 and args1 == args2:
+        if flexible_equal(result1, result2) and flexible_equal(args1, args2):
             debug("Functions equivalent")
             return (VerificationStatus.CONFIRMED, None)
         debug("Functions differ")
diff --git a/crosshair/diff_behavior_test.py b/crosshair/diff_behavior_test.py
index 3e965d68..a441d0fc 100644
--- a/crosshair/diff_behavior_test.py
+++ b/crosshair/diff_behavior_test.py
@@ -146,6 +146,18 @@ def f(a: Optional[Callable[[int], int]]):
     assert diffs == []
 
 
+def test_diff_behavior_nan() -> None:
+    def f(x: float):
+        return x
+
+    diffs = diff_behavior(
+        FunctionInfo.from_fn(f),
+        FunctionInfo.from_fn(f),
+        DEFAULT_OPTIONS,
+    )
+    assert diffs == []
+
+
 if __name__ == "__main__":
     if ("-v" in sys.argv) or ("--verbose" in sys.argv):
         set_debug(True)
diff --git a/crosshair/fuzz_core_test.py b/crosshair/fuzz_core_test.py
index 5bf99b82..5abf4b4b 100644
--- a/crosshair/fuzz_core_test.py
+++ b/crosshair/fuzz_core_test.py
@@ -45,6 +45,7 @@
     StateSpaceContext,
 )
 from crosshair.stubs_parser import signature_from_stubs
+from crosshair.test_util import flexible_equal
 from crosshair.tracers import COMPOSITE_TRACER, NoTracing, ResumedTracing
 from crosshair.util import CrosshairUnsupported, debug, type_args_of
 
@@ -300,7 +301,7 @@ def symbolic_checker(
             postexec_symbolic_args = deep_realize(postexec_symbolic_args)
             symbolic_ret = deep_realize(symbolic_ret)
             symbolic_exc = deep_realize(symbolic_exc)
-            rets_differ = realize(bool(literal_ret != symbolic_ret))
+            rets_differ = not realize(flexible_equal(literal_ret, symbolic_ret))
             postexec_args_differ = realize(
                 bool(postexec_literal_args != postexec_symbolic_args)
             )
diff --git a/crosshair/test_util.py b/crosshair/test_util.py
index 6173b3d1..0b47b9ff 100644
--- a/crosshair/test_util.py
+++ b/crosshair/test_util.py
@@ -1,9 +1,9 @@
 import pathlib
 import sys
-import traceback
+from collections.abc import Container
 from copy import deepcopy
 from dataclasses import dataclass, replace
-from typing import Callable, Iterable, List, Mapping, Optional, Sequence, Set, Tuple
+from typing import Callable, Iterable, List, Mapping, Optional, Sequence, Tuple
 
 from crosshair.core import (
     AnalysisMessage,
@@ -21,6 +21,7 @@
     ch_stack,
     debug,
     in_debug,
+    is_iterable,
     is_pure_python,
     name_of_type,
 )
@@ -128,6 +129,27 @@ def flexible_equal(a, b):
         return True
     if a != a and b != b:  # handle float('nan')
         return True
+    if (
+        is_iterable(a)
+        and not isinstance(a, Container)
+        and is_iterable(b)
+        and not isinstance(b, Container)
+    ):  # unsized iterables compare by contents
+        a, b = list(a), list(b)
+    if type(a) == type(b):
+        # Recursively apply flexible_equal for most containers:
+        if isinstance(a, Mapping):
+            if len(a) != len(b):
+                return False
+            for k, v in a.items():
+                if not flexible_equal(v, b[k]):
+                    return False
+            return True
+        if isinstance(a, Container) and not isinstance(a, (str, bytes)):
+            if len(a) != len(b):
+                return False
+            return all(flexible_equal(ai, bi) for ai, bi in zip(a, b))
+
     return a == b
 
 
diff --git a/crosshair/test_util_test.py b/crosshair/test_util_test.py
new file mode 100644
index 00000000..02bfc1d6
--- /dev/null
+++ b/crosshair/test_util_test.py
@@ -0,0 +1,16 @@
+from crosshair.test_util import flexible_equal
+
+
+def test_flexible_equal():
+    assert float("nan") != float("nan")
+    assert flexible_equal(float("nan"), float("nan"))
+    assert flexible_equal((42, float("nan")), (42, float("nan")))
+    assert not flexible_equal([float("nan"), 11], [float("nan"), 22])
+
+    def gen():
+        yield 11
+        yield 22
+
+    assert flexible_equal(gen(), iter([11, 22]))
+    assert not flexible_equal(gen(), iter([11, 22, 33]))
+    assert not flexible_equal(gen(), iter([11]))