diff --git a/parso/normalizer.py b/parso/normalizer.py
index 509cf6d..9607749 100644
--- a/parso/normalizer.py
+++ b/parso/normalizer.py
@@ -1,4 +1,5 @@
 from contextlib import contextmanager
+from functools import total_ordering
 
 
 class Normalizer(object):
@@ -15,7 +16,8 @@ class Normalizer(object):
 
     def add_issue(self, code, message, node):
         issue = Issue(node, code, message)
-        self.issues.append(issue)
+        if issue not in self.issues:
+            self.issues.append(issue)
         return True
 
 
@@ -53,6 +55,16 @@ class Issue(object):
         self.message = message
         self.start_pos = node.start_pos
 
+    def __eq__(self, other):
+        return self.start_pos == other.start_pos and self.code == other.code
+
+    def __ne__(self, other):
+        return not self.__eq__(other)
+
+    def __hash__(self):
+        return hash((self.code, self.start_pos))
+
+
 
 class Rule(object):
     error_code = None
diff --git a/parso/python/normalizer.py b/parso/python/normalizer.py
index bf8971b..c09c4c3 100644
--- a/parso/python/normalizer.py
+++ b/parso/python/normalizer.py
@@ -141,9 +141,11 @@ class PEP8Normalizer(Normalizer):
     def __init__(self, config):
         super(PEP8Normalizer, self).__init__(config)
         self._previous_leaf = None
+        self._actual_previous_leaf = None
         self._on_newline = True
         self._newline_count = 0
         self._wanted_newline_count = None
+        self._max_new_lines_in_prefix = 0
         self._new_statement = True
         self._implicit_indentation_possible = False
         # The top of stack of the indentation nodes.
@@ -264,6 +266,9 @@ class PEP8Normalizer(Normalizer):
         return int(suite_node.parent is None) + 1
 
     def _reset_newlines(self, spacing, actual_leaf, is_comment=False):
+        self._max_new_lines_in_prefix = \
+            max(self._max_new_lines_in_prefix, self._newline_count)
+
         wanted = self._wanted_newline_count
         if wanted is not None:
             # Need to substract one
@@ -280,6 +285,27 @@ class PEP8Normalizer(Normalizer):
             else:
                 self._wanted_newline_count = None
 
+        if not is_comment:
+            wanted = self._get_wanted_blank_lines_count()
+            actual = self._max_new_lines_in_prefix - 1
+
+            val = actual_leaf.value
+            needs_lines = (
+                val == '@' and actual_leaf.parent.type == 'decorator'
+                or val == 'class'
+                or val == 'async' and actual_leaf.get_next_leaf() == 'def'
+                or val == 'def' and self._actual_previous_leaf != 'async'
+            )
+            if needs_lines and actual < wanted:
+                # The first leaf should not be added.
+                if self._actual_previous_leaf is not None:
+                    code = 302 if wanted == 2 else 301
+                    message = "expected %s blank line, found %s" \
+                        % (wanted, actual)
+                    self.add_issue(code, message, spacing)
+
+            self._max_new_lines_in_prefix = 0
+
         self._newline_count = 0
 
     def normalize(self, leaf):
@@ -306,6 +332,9 @@ class PEP8Normalizer(Normalizer):
 
         if not self._new_statement:
             self._reset_newlines(part, leaf)
+            self._max_blank_lines = 0
+
+        self._actual_previous_leaf = leaf
 
         return x
 
diff --git a/test/normalizer_issue_files/E30.py b/test/normalizer_issue_files/E30.py
index 0bb8cd6..2383a32 100644
--- a/test/normalizer_issue_files/E30.py
+++ b/test/normalizer_issue_files/E30.py
@@ -146,14 +146,14 @@ if a():
     a()
 
 
-#: E301+3:4
+#: E301+2
 def a():
     x = 1
     def b():
         pass
 
 
-#: E301+3:4 E301+5:8
+#: E301+2 E301+4
 def a():
     x = 2
     def b():
@@ -162,7 +162,7 @@ def a():
             pass
 
 
-#: E301+4 E301+6
+#: E301+2 E301+4 E301+5
 def a():
     x = 1
     class C: