diff --git a/lark/lark.py b/lark/lark.py
index ed1dfbc..4aa9e7e 100644
--- a/lark/lark.py
+++ b/lark/lark.py
@@ -288,7 +288,12 @@ class Lark(Serialize):
             if self.options.parser == 'lalr':
                 self.options.lexer = 'contextual'
             elif self.options.parser == 'earley':
-                self.options.lexer = 'dynamic'
+                if self.options.postlex is not None:
+                    logger.info("postlex can't be used with the dynamic lexer, so we use standard instead. "
+                                "Consider using lalr with contextual instead of earley")
+                    self.options.lexer = 'standard'
+                else:
+                    self.options.lexer = 'dynamic'
             elif self.options.parser == 'cyk':
                 self.options.lexer = 'standard'
             else:
@@ -298,6 +303,8 @@ class Lark(Serialize):
             assert issubclass(lexer, Lexer)     # XXX Is this really important? Maybe just ensure interface compliance
         else:
             assert_config(lexer, ('standard', 'contextual', 'dynamic', 'dynamic_complete'))
+            if self.options.postlex is not None and 'dynamic' in lexer:
+                raise ConfigurationError("Can't use postlex with a dynamic lexer. Use standard or contextual instead")
 
         if self.options.ambiguity == 'auto':
             if self.options.parser == 'earley':
diff --git a/lark/parser_frontends.py b/lark/parser_frontends.py
index 5acbbeb..04d38a4 100644
--- a/lark/parser_frontends.py
+++ b/lark/parser_frontends.py
@@ -83,6 +83,7 @@ class ParsingFrontend(Serialize):
         lexer_type = lexer_conf.lexer_type
         self.skip_lexer = False
         if lexer_type in ('dynamic', 'dynamic_complete'):
+            assert lexer_conf.postlex is None
             self.skip_lexer = True
             return