diff --git a/jedi/evaluate/pep0484.py b/jedi/evaluate/pep0484.py
index 7519ce3b..10edcb8e 100644
--- a/jedi/evaluate/pep0484.py
+++ b/jedi/evaluate/pep0484.py
@@ -80,7 +80,7 @@ def _fix_forward_reference(context, node):
         return node
 
 
-def _split_mypy_param_declaration(decl_text):
+def _split_comment_param_declaration(decl_text):
     """
     Split decl_text on commas, but group generic expressions
     together.
@@ -99,9 +99,14 @@ def _split_mypy_param_declaration(decl_text):
         return [node.get_code().strip()]
 
     params = []
-    for child in node.children:
-        if child.type in ['name', 'atom_expr', 'power']:
-            params.append(child.get_code().strip())
+    try:
+        children = node.children
+    except AttributeError:
+        return []
+    else:
+        for child in children:
+            if child.type in ['name', 'atom_expr', 'power']:
+                params.append(child.get_code().strip())
 
     return params
 
@@ -128,7 +133,7 @@ def infer_param(execution_context, param):
         match = re.match(r"^#\s*type:\s*\(([^#]*)\)\s*->", comment)
         if not match:
             return NO_CONTEXTS
-        params_comments = _split_mypy_param_declaration(match.group(1))
+        params_comments = _split_comment_param_declaration(match.group(1))
 
         # Find the specific param being investigated
         index = all_params.index(param)
diff --git a/test/completion/pep0484_comments.py b/test/completion/pep0484_comments.py
index 181b698a..816cc736 100644
--- a/test/completion/pep0484_comments.py
+++ b/test/completion/pep0484_comments.py
@@ -157,11 +157,6 @@ x = UNKNOWN_NAME2  # type: str
 #? str()
 x
 
-def x(a, b):
-    # type: ([) -> a
-    #?
-    a
-
 class Cat(object):
     def __init__(self, age, friends, name):
         # type: (int, List[Dog], str) -> None
@@ -172,3 +167,14 @@ class Cat(object):
 cat = Cat(UNKNOWN_NAME4, UNKNOWN_NAME5, UNKNOWN_NAME6)
 #? str()
 cat.name
+
+
+# Check potential errors
+def x(a, b):
+    # type: ([) -> a
+    #?
+    a
+def x(a, b):
+    # type: (1) -> a
+    #?
+    a