diff --git a/python/tox.ini b/python/tox.ini
index e82beade4..64159f888 100644
--- a/python/tox.ini
+++ b/python/tox.ini
@@ -8,6 +8,10 @@ passenv = APPVEYOR*
           SSL_CERT_FILE
           TEST_MARKER
           TRAVIS*
+          LDFLAGS
+          CPPFLAGS
+          CC
+          CXX
 setenv = COVERAGE_FILE={toxworkdir}/.coverage.{envname}
 usedevelop = True
 deps = -rrequirements.txt