diff --git a/tests/__init__.py b/tests/__init__.py
index d017afad4..d940f28ea 100644
--- a/tests/__init__.py
+++ b/tests/__init__.py
@@ -13,6 +13,14 @@ os.environ['http_proxy'] = ''
 os.environ['https_proxy'] = ''
 os.environ['ftp_proxy'] = ''
 
+# Absolutize paths to coverage config and output file because tests that
+# spawn subprocesses also changes current working directory.
+_sourceroot = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+if 'COV_CORE_CONFIG' in os.environ:
+    os.environ['COVERAGE_FILE'] = os.path.join(_sourceroot, '.coverage')
+    os.environ['COV_CORE_CONFIG'] = os.path.join(_sourceroot,
+                                                 os.environ['COV_CORE_CONFIG'])
+
 try:
     import unittest.mock as mock
 except ImportError: