diff --git a/modelscan/tools/picklescanner.py b/modelscan/tools/picklescanner.py
index 2a96c31..0dbe6d2 100644
--- a/modelscan/tools/picklescanner.py
+++ b/modelscan/tools/picklescanner.py
@@ -52,7 +52,7 @@ def _list_globals(
 ) -> Set[Tuple[str, str]]:
     globals: Set[Any] = set()
 
-    memo: Dict[int, str] = {}
+    memo: Dict[Union[int, str], str] = {}
     # Scan the data for pickle buffers, stopping when parsing fails or stops making progress
     last_byte = b"dummy"
     while last_byte != b"":
@@ -72,10 +72,11 @@ def _list_globals(
             op_name = op[0].name
             op_value: str = op[1]
 
-            if op_name in ["MEMOIZE", "PUT", "BINPUT", "LONG_BINPUT"] and n > 0:
+            if op_name == "MEMOIZE" and n > 0:
                 memo[len(memo)] = ops[n - 1][1]
-
-            if op_name in ["GLOBAL", "INST"]:
+            elif op_name in ["PUT", "BINPUT", "LONG_BINPUT"] and n > 0:
+                memo[op_value] = ops[n - 1][1]
+            elif op_name in ("GLOBAL", "INST"):
                 globals.add(tuple(op_value.split(" ", 1)))
             elif op_name == "STACK_GLOBAL":
                 values: List[str] = []
diff --git a/tests/test_modelscan.py b/tests/test_modelscan.py
index 3464dd4..209015d 100644
--- a/tests/test_modelscan.py
+++ b/tests/test_modelscan.py
@@ -168,6 +168,36 @@ def file_path(tmp_path_factory: Any) -> Any:
     initialize_pickle_file(f"{tmp}/data/malicious8.pkl", Malicious7(), 4)
     initialize_pickle_file(f"{tmp}/data/malicious9.pkl", Malicious8(), 4)
 
+    # Malicious Pickle from Capture-the-Flag challenge 'Misc/Safe Pickle' at https://imaginaryctf.org/Challenges
+    # GitHub Issue: https://github.com/mmaitre314/picklescan/issues/22
+    initialize_data_file(
+        f"{tmp}/data/malicious11.pkl",
+        b"".join(
+            [
+                pickle.UNICODE + b"os\n",
+                pickle.PUT + b"2\n",
+                pickle.POP,
+                pickle.UNICODE + b"system\n",
+                pickle.PUT + b"3\n",
+                pickle.POP,
+                pickle.UNICODE + b"torch\n",
+                pickle.PUT + b"0\n",
+                pickle.POP,
+                pickle.UNICODE + b"LongStorage\n",
+                pickle.PUT + b"1\n",
+                pickle.POP,
+                pickle.GET + b"2\n",
+                pickle.GET + b"3\n",
+                pickle.STACK_GLOBAL,
+                pickle.MARK,
+                pickle.UNICODE + b"cat flag.txt\n",
+                pickle.TUPLE,
+                pickle.REDUCE,
+                pickle.STOP,
+            ]
+        ),
+    )
+
     initialize_zip_file(
         f"{tmp}/data/malicious1.zip",
         "data.pkl",
@@ -603,6 +633,17 @@ def test_scan_pickle_operators(file_path: Any) -> None:
     malicious10.scan(Path(f"{file_path}/data/malicious10.pkl"))
     assert malicious10.issues.all_issues == expected_malicious10
 
+    expected_malicious11 = [
+        Issue(
+            IssueCode.UNSAFE_OPERATOR,
+            IssueSeverity.CRITICAL,
+            OperatorIssueDetails("os", "system", f"{file_path}/data/malicious11.pkl"),
+        )
+    ]
+    malicious11 = ModelScan()
+    malicious11.scan(Path(f"{file_path}/data/malicious11.pkl"))
+    assert malicious11.issues.all_issues == expected_malicious11
+
 
 def test_scan_directory_path(file_path: str) -> None:
     expected = {
@@ -761,6 +802,11 @@ def test_scan_directory_path(file_path: str) -> None:
                 "__builtin__", "exec", f"{file_path}/data/malicious10.pkl"
             ),
         ),
+        Issue(
+            IssueCode.UNSAFE_OPERATOR,
+            IssueSeverity.CRITICAL,
+            OperatorIssueDetails("os", "system", f"{file_path}/data/malicious11.pkl"),
+        ),
     }
     ms = ModelScan()
     p = Path(f"{file_path}/data/")