diff --git a/test/functional/test_framework/cdefs.py b/test/functional/test_framework/cdefs.py
index e9867ec41..f1dcf0760 100644
--- a/test/functional/test_framework/cdefs.py
+++ b/test/functional/test_framework/cdefs.py
@@ -1,105 +1,96 @@
 #!/usr/bin/env python3
 # Copyright (c) 2017 The Bitcoin developers
 # Distributed under the MIT software license, see the accompanying
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 """
 Imports some application default values from source files outside the test
 framework, and defines equivalents of consensus parameters for the test
 framework.
 """
 
 import os
 import re
 
 
-def get_srcdir(calling_script=None):
+def get_srcdir():
     """
     Try to find out the base folder containing the 'src' folder.
     If SRCDIR is set it does a sanity check and returns that.
     Otherwise it goes on a search and rescue mission.
 
     Returns None if it cannot find a suitable folder.
     """
     def contains_src(path_to_check):
         if not path_to_check:
             return False
         else:
             cand_path = os.path.join(path_to_check, 'src')
             return os.path.exists(cand_path) and os.path.isdir(cand_path)
 
     srcdir = os.environ.get('SRCDIR', '')
     if contains_src(srcdir):
         return srcdir
 
-    # If we have a caller, try to guess from its location where the
-    # top level might be.
-    if calling_script:
-        caller_basedir = os.path.dirname(
-            os.path.dirname(os.path.dirname(calling_script)))
-        if caller_basedir != '' and contains_src(os.path.abspath(caller_basedir)):
-            return os.path.abspath(caller_basedir)
-
     # Try to work it based out on main module
-    # We might expect the caller to be rpc-tests.py or a test script
-    # itself.
     import sys
     mainmod = sys.modules['__main__']
     mainmod_path = getattr(mainmod, '__file__', '')
     if mainmod_path and mainmod_path.endswith('.py'):
-        maybe_top = os.path.dirname(
-            os.path.dirname(os.path.dirname(mainmod_path)))
-        if contains_src(os.path.abspath(maybe_top)):
-            return os.path.abspath(maybe_top)
+        maybe_top = mainmod_path
+        while maybe_top != '/':
+            maybe_top = os.path.abspath(os.path.dirname(maybe_top))
+            if contains_src(maybe_top):
+                return maybe_top
 
     # No luck, give up.
     return None
 
 
 # Slurp in consensus.h contents
 _consensus_h_fh = open(os.path.join(get_srcdir(), 'src', 'consensus',
                                     'consensus.h'), 'rt')
 _consensus_h_contents = _consensus_h_fh.read()
 _consensus_h_fh.close()
 
 # This constant is currently needed to evaluate some that are formulas
 ONE_MEGABYTE = 1000000
 
 # Extract relevant default values parameters
 
 # The maximum allowed block size before the fork
 LEGACY_MAX_BLOCK_SIZE = ONE_MEGABYTE
 
 # Default setting for maximum allowed size for a block, in bytes
 DEFAULT_MAX_BLOCK_SIZE = eval(
     re.search(r'DEFAULT_MAX_BLOCK_SIZE = (.+);',
               _consensus_h_contents).group(1))
 
 # The following consensus parameters should not be automatically imported.
 # They *should* cause test failures if application code is changed in ways
 # that violate current consensus.
 
 # The maximum allowed number of signature check operations per MB in a block
 # (network rule)
 MAX_BLOCK_SIGOPS_PER_MB = 20000
 
 # The maximum allowed number of signature check operations per transaction
 # (network rule)
 MAX_TX_SIGOPS_COUNT = 20000
 
 # The maximum number of sigops we're willing to relay/mine in a single tx
 # (policy.h constant)
 MAX_STANDARD_TX_SIGOPS = MAX_TX_SIGOPS_COUNT // 5
 
 # Coinbase transaction outputs can only be spent after this number of new
 # blocks (network rule)
 COINBASE_MATURITY = 100
 
 # Anti replay OP_RETURN commitment.
 ANTI_REPLAY_COMMITMENT = b"Bitcoin: A Peer-to-Peer Electronic Cash System"
 
 if __name__ == "__main__":
     # Output values if run standalone to verify
     print("DEFAULT_MAX_BLOCK_SIZE = %d (bytes)" % DEFAULT_MAX_BLOCK_SIZE)
     print("MAX_BLOCK_SIGOPS_PER_MB = %d (sigops)" % MAX_BLOCK_SIGOPS_PER_MB)
     print("MAX_TX_SIGOPS_COUNT = %d (sigops)" % MAX_TX_SIGOPS_COUNT)
     print("COINBASE_MATURITY = %d (blocks)" % COINBASE_MATURITY)