diff --git a/lark/load_grammar.py b/lark/load_grammar.py
index 786b4a3..01739a8 100644
--- a/lark/load_grammar.py
+++ b/lark/load_grammar.py
@@ -24,6 +24,8 @@ inline_args = v_args(inline=True)
 __path__ = os.path.dirname(__file__)
 IMPORT_PATHS = [os.path.join(__path__, 'grammars')]
 
+EXT = '.lark'
+
 _RE_FLAGS = 'imslux'
 
 def is_terminal(sym):
@@ -139,16 +141,16 @@ RULES = {
     'ignore': ['_IGNORE expansions _NL'],
     'declare': ['_DECLARE _declare_args _NL'],
     'import': ['_IMPORT _import_path _NL',
-               '_IMPORT _import_path _LPAR list_name _RPAR _NL',
+               '_IMPORT _import_path _LPAR name_list _RPAR _NL',
                '_IMPORT _import_path _TO TERMINAL _NL'],
 
-    '_import_path': ['import_common', 'import_rel'],
-    'import_common': ['_import_args'],
+    '_import_path': ['import_lib', 'import_rel'],
+    'import_lib': ['_import_args'],
     'import_rel': ['_DOT _import_args'],
     '_import_args': ['name', '_import_args _DOT name'],
 
-    'list_name': ['_list_name'],
-    '_list_name': ['name', '_list_name _COMMA name'],
+    'name_list': ['_name_list'],
+    '_name_list': ['name', '_name_list _COMMA name'],
 
     '_declare_args': ['name', '_declare_args name'],
     'literal': ['REGEXP', 'STRING'],
@@ -506,25 +508,19 @@ class Grammar:
 
 
 _imported_grammars = {}
-def import_grammar(grammar_path, base_path=None):
+def import_grammar(grammar_path, base_paths=[]):
     if grammar_path not in _imported_grammars:
-        if base_path is None:
-            import_paths = IMPORT_PATHS
-        else:
-            import_paths = [base_path] + IMPORT_PATHS
-        found = False
+        import_paths = base_paths + IMPORT_PATHS
         for import_path in import_paths:
-            try:
+            with suppress(IOError):
                 with open(os.path.join(import_path, grammar_path)) as f:
                     text = f.read()
                 grammar = load_grammar(text, grammar_path)
                 _imported_grammars[grammar_path] = grammar
-                found = True
                 break
-            except FileNotFoundError:
-                pass
-        if not found:
-            raise FileNotFoundError(grammar_path)
+        else:
+            open(grammar_path)
+            assert False
 
     return _imported_grammars[grammar_path]
 
@@ -640,18 +636,25 @@ class GrammarLoader:
                 t ,= stmt.children
                 ignore.append(t)
             elif stmt.data == 'import':
-                dotted_path = stmt.children[0].children
+                if len(stmt.children) > 1:
+                    path_node, arg1 = stmt.children
+                else:
+                    path_node ,= stmt.children
+                    arg1 = None
+
+                dotted_path = path_node.children
 
-                if len(stmt.children) > 1 and hasattr(stmt.children[1], 'children'):  # Multi import
-                    names = stmt.children[1].children
+                if isinstance(arg1, Tree):  # Multi import
+                    names = arg1.children
                     aliases = names  # Can't have aliased multi import, so all aliases will be the same as names
-                    grammar_path = os.path.join(*dotted_path) + '.lark'
                 else:  # Single import
                     names = [dotted_path[-1]]  # Get name from dotted path
-                    aliases = [stmt.children[1] if len(stmt.children) > 1 else dotted_path[-1]]  # Aliases if exist
-                    grammar_path = os.path.join(*dotted_path[:-1]) + '.lark'  # Exclude name from grammar path
+                    aliases = [arg1] if arg1 else names  # Aliases if exist
+                    dotted_path = dotted_path[:-1]
+
+                grammar_path = os.path.join(*dotted_path) + EXT
 
-                if stmt.children[0].data == 'import_common':  # Regular import
+                if path_node.data == 'import_lib':  # Import from library
                     g = import_grammar(grammar_path)
                 else:  # Relative import
                     if grammar_name == '<string>':  # Import relative to script file path if grammar is coded in script
@@ -659,7 +662,7 @@ class GrammarLoader:
                     else:
                         base_file = grammar_name  # Import relative to grammar file path if external grammar file
                     base_path = os.path.split(base_file)[0]
-                    g = import_grammar(grammar_path, base_path=base_path)
+                    g = import_grammar(grammar_path, base_paths=[base_path])
 
                 for name, alias in zip(names, aliases):
                     token_options = dict(g.token_defs)[name]
diff --git a/tests/test_parser.py b/tests/test_parser.py
index 0cb74e2..c4d7147 100644
--- a/tests/test_parser.py
+++ b/tests/test_parser.py
@@ -976,6 +976,20 @@ def _make_parser_test(LEXER, PARSER):
             x = l.parse('12 capybaras')
             self.assertEqual(x.children, ['12', 'capybaras'])
 
+        def test_import_errors(self):
+            grammar = """
+            start: NUMBER WORD
+
+            %import .grammars.bad_test.NUMBER
+            """
+            self.assertRaises(IOError, _Lark, grammar)
+
+            grammar = """
+            start: NUMBER WORD
+
+            %import bad_test.NUMBER
+            """
+            self.assertRaises(IOError, _Lark, grammar)
 
         @unittest.skipIf(PARSER != 'earley', "Currently only Earley supports priority in rules")
         def test_earley_prioritization(self):