diff --git a/enaml/core/code_generator.py b/enaml/core/code_generator.py
index dc87bafb3..66e7ffcd9 100644
--- a/enaml/core/code_generator.py
+++ b/enaml/core/code_generator.py
@@ -588,10 +588,14 @@ def rewrite_to_fast_locals(self, local_names):
         stored_names = set()
         code_ops = self.code_ops
         for idx, instr in enumerate(code_ops):
+            if not isinstance(instr, bc.Instr):
+                continue
             if instr.name == "STORE_NAME":
                 stored_names.add(instr.arg)
                 instr.name = "STORE_FAST"
         for idx, instr in enumerate(code_ops):
+            if not isinstance(instr, bc.Instr):
+                continue
             i_name = instr.name
             if i_name == "LOAD_NAME":
                 i_arg = instr.arg
diff --git a/releasenotes.rst b/releasenotes.rst
index 2120ad306..536b401b9 100644
--- a/releasenotes.rst
+++ b/releasenotes.rst
@@ -3,6 +3,10 @@ Enaml Release Notes
 
 Dates are written as DD/MM/YYYY
 
+0.17.1 - unreleased
+-------------------
+- fix possible error in rewrite fast locals when using templates on 3.12 PR #550
+
 0.17.0 - 20/11/2023
 -------------------
 - support for Python 3.12 PR #535
diff --git a/tests/test_template.py b/tests/test_template.py
index 7cfeeae97..b58c1987c 100644
--- a/tests/test_template.py
+++ b/tests/test_template.py
@@ -241,6 +241,24 @@ def test_syntax_20():
     compile_source(source, 'Main')
 
 
+def test_syntax_21():
+    source = dedent("""\
+    template Other(*Args):
+        Slider:
+            pass
+
+    template Main(Model):
+        const args = [
+            m for m in Model.members().values()
+            if isinstance(m, Float)
+        ]
+        Other(args): *all:
+            pass
+
+    """)
+    compile_source(source, 'Main')
+
+
 #------------------------------------------------------------------------------
 # Bad Template Syntax
 #------------------------------------------------------------------------------