diff --git a/src/arch/z80/peephole/evaluator.py b/src/arch/z80/peephole/evaluator.py
index 29156458..82c57632 100644
--- a/src/arch/z80/peephole/evaluator.py
+++ b/src/arch/z80/peephole/evaluator.py
@@ -195,7 +195,7 @@ def __init__(self, expression):
             expression[2] = Evaluator(expression[2])
         else:  # It's a list
             assert len(expression) % 2  # Must be odd length
-            assert all(x == FN.OP_COMMA for i, x in enumerate(expression) if i % 2)
+            assert all(x == FN.OP_COMMA for i, x in enumerate(expression) if i % 2), f"Invalid expression {expression}"
             self.expression = [Evaluator(x) if not i % 2 else x for i, x in enumerate(expression)]
 
     @staticmethod
diff --git a/src/arch/z80/peephole/parser.py b/src/arch/z80/peephole/parser.py
index 47332f3b..99d2958e 100644
--- a/src/arch/z80/peephole/parser.py
+++ b/src/arch/z80/peephole/parser.py
@@ -161,6 +161,10 @@ def parse_ifline(if_line: str, lineno: int) -> TreeType | None:
                 errmsg.warning(lineno, "missing element in list")
                 return None
 
+            if any(x != FN.OP_COMMA for i, x in enumerate(expr) if i % 2):
+                errmsg.warning(lineno, f"Invalid list {expr}")
+                return None
+
             stack[-1].append(expr)
             expr = stack.pop()
         else:
diff --git a/tests/arch/zx48k/peephole/test_parser.py b/tests/arch/zx48k/peephole/test_parser.py
index 844f2b24..54762b2e 100644
--- a/tests/arch/zx48k/peephole/test_parser.py
+++ b/tests/arch/zx48k/peephole/test_parser.py
@@ -399,14 +399,8 @@ def test_parse_if_must_start_in_a_new_line(self):
     def test_parse_with_ending_binary_error(self):
         result = parser.parse_str(
             """
-            ;; Remove the boolean normalization if it's done after calling
-            ;; certain routines that return the bool result already normalized.
-
-            ;; The sequence
-            ;;   sub 1
-            ;;   sbc a, a
-            ;;   inc a
-            ;; can be removed
+            ;; Sample Comment
+            ;;
 
             OLEVEL: 1
             OFLAG: 20
@@ -428,15 +422,6 @@ def test_parse_with_ending_binary_error(self):
     def test_parse_with_comma_error(self):
         result = parser.parse_str(
             """
-            ;; Remove the boolean normalization if it's done after calling
-            ;; certain routines that return the bool result already normalized.
-
-            ;; The sequence
-            ;;   sub 1
-            ;;   sbc a, a
-            ;;   inc a
-            ;; can be removed
-
             OLEVEL: 1
             OFLAG: 20
 
@@ -458,15 +443,6 @@ def test_parse_with_comma_error(self):
     def test_parse_with_nested_comma_error(self):
         result = parser.parse_str(
             """
-            ;; Remove the boolean normalization if it's done after calling
-            ;; certain routines that return the bool result already normalized.
-
-            ;; The sequence
-            ;;   sub 1
-            ;;   sbc a, a
-            ;;   inc a
-            ;; can be removed
-
             OLEVEL: 1
             OFLAG: 20
 
@@ -484,3 +460,43 @@ def test_parse_with_nested_comma_error(self):
             """
         )
         assert result is None
+
+    def test_parse_with_list_error(self):
+        result = parser.parse_str(
+            """
+            OLEVEL: 1
+            OFLAG: 20
+
+            REPLACE {{
+              $1
+            }}
+
+            WITH {{
+            }}
+
+            IF {{
+              $1 IN ("x", "y" . "pera")
+            }}
+            """
+        )
+        assert result is None
+
+    def test_parse_with_list_error2(self):
+        result = parser.parse_str(
+            """
+            OLEVEL: 1
+            OFLAG: 20
+
+            REPLACE {{
+              $1
+            }}
+
+            WITH {{
+            }}
+
+            IF {{
+              $1 IN ("x", , , "pera")
+            }}
+            """
+        )
+        assert result is None