diff --git a/make/py-defs.mk b/make/py-defs.mk
index 894a919d..72041d06 100644
--- a/make/py-defs.mk
+++ b/make/py-defs.mk
@@ -26,7 +26,7 @@ else
   PY_INSTALL_MOD     ?= $(PY_INSTALL_PKG_MOD)
 endif
 PY_MOD               ?= $(subst /,.,$(PY_INSTALL_MOD))
-PY_INSTALL_DIR        = $(ENV_PREFIX)$(PY_SITE_PACKAGES_PATH)/$(patsubst .,/,$(PY_INSTALL_MOD))
+PY_INSTALL_DIR       ?= $(ENV_PREFIX)$(PY_SITE_PACKAGES_PATH)/$(patsubst .,/,$(PY_INSTALL_MOD))
 PY_INSTALLED_REG      = $(addprefix $(PY_INSTALL_DIR)/,$(PY_ALL_PY) $(PY_PYC))
 
 empty                :=