diff --git a/tests/run-tests.py b/tests/run-tests.py
--- a/tests/run-tests.py
+++ b/tests/run-tests.py
@@ -1211,6 +1211,10 @@ def main():
             # can't remove on solaris
             os.environ[k] = ''
             del os.environ[k]
+    if 'HG' in os.environ:
+        # can't remove on solaris
+        os.environ['HG'] = ''
+        del os.environ['HG']
 
     global TESTDIR, HGTMP, INST, BINDIR, PYTHONDIR, COVERAGE_FILE
     TESTDIR = os.environ["TESTDIR"] = os.getcwd()