diff --git a/contrib/devtools/test-security-check.py b/contrib/devtools/test-security-check.py
index 90268740c60..1390e310f28 100755
--- a/contrib/devtools/test-security-check.py
+++ b/contrib/devtools/test-security-check.py
@@ -28,7 +28,7 @@ def clean_files(source, executable):
     os.remove(source)
     os.remove(executable)
 
-def call_security_check(cc, source, executable, options):
+def call_security_check(cc: str, source: str, executable: str, options) -> tuple:
     # This should behave the same as AC_TRY_LINK, so arrange well-known flags
     # in the same order as autoconf would.
     #
diff --git a/test/functional/p2p_message_capture.py b/test/functional/p2p_message_capture.py
index 62ff4da8fd1..691a0b6409c 100755
--- a/test/functional/p2p_message_capture.py
+++ b/test/functional/p2p_message_capture.py
@@ -19,7 +19,7 @@ TIME_SIZE = 8
 LENGTH_SIZE = 4
 MSGTYPE_SIZE = 12
 
-def mini_parser(dat_file):
+def mini_parser(dat_file: str) -> None:
     """Parse a data file created by CaptureMessageToFile.
 
     From the data file we'll only check the structure.
diff --git a/test/functional/test_framework/test_framework.py b/test/functional/test_framework/test_framework.py
index d3aae3fb9a2..73e7516ea7e 100755
--- a/test/functional/test_framework/test_framework.py
+++ b/test/functional/test_framework/test_framework.py
@@ -92,7 +92,7 @@ class BitcoinTestFramework(metaclass=BitcoinTestMetaClass):
 
     This class also contains various public and private helper methods."""
 
-    def __init__(self):
+    def __init__(self) -> None:
         """Sets test framework defaults. Do not override this method. Instead, override the set_test_params() method"""
         self.chain: str = 'regtest'
         self.setup_clean_chain: bool = False