diff --git a/nbconvert/nbconvertapp.py b/nbconvert/nbconvertapp.py
index 78a0724ea..0b2a68f50 100755
--- a/nbconvert/nbconvertapp.py
+++ b/nbconvert/nbconvertapp.py
@@ -357,6 +357,8 @@ def initialize(self, argv=None):
 
         self.init_syspath()
         super().initialize(argv)
+        if hasattr(self, "load_config_environ"):
+            self.load_config_environ()
         self.init_notebooks()
         self.init_writer()
         self.init_postprocessor()
@@ -655,6 +657,8 @@ def initialize(self, argv=None):
         self.config.QtPDFExporter.paginate = False
 
         super().initialize(argv)
+        if hasattr(self, "load_config_environ"):
+            self.load_config_environ()
 
     @default("export_format")
     def _default_export_format(self):