diff --git a/conftest.py b/conftest.py
index f69ad9e..6fe3544 100644
--- a/conftest.py
+++ b/conftest.py
@@ -58,7 +58,9 @@ def pytest_generate_tests(metafunc):
     elif 'each_py3_version' in metafunc.fixturenames:
         metafunc.parametrize('each_py3_version', VERSIONS_3)
     elif 'version_ge_py36' in metafunc.fixturenames:
-        metafunc.parametrize('version_ge_py36', ['3.6', '3.7'])
+        metafunc.parametrize('version_ge_py36', ['3.6', '3.7', '3.8'])
+    elif 'version_ge_py38' in metafunc.fixturenames:
+        metafunc.parametrize('version_ge_py38', ['3.8'])
 
 
 class NormalizerIssueCase(object):
diff --git a/parso/python/tokenize.py b/parso/python/tokenize.py
index 48d128b..ff0bd21 100644
--- a/parso/python/tokenize.py
+++ b/parso/python/tokenize.py
@@ -314,17 +314,19 @@ class FStringNode(object):
 
 def _close_fstring_if_necessary(fstring_stack, string, start_pos, additional_prefix):
     for fstring_stack_index, node in enumerate(fstring_stack):
-        if string.startswith(node.quote):
+        lstriped_string = string.lstrip()
+        len_lstrip = len(string) - len(lstriped_string)
+        if lstriped_string.startswith(node.quote):
             token = PythonToken(
                 FSTRING_END,
                 node.quote,
                 start_pos,
-                prefix=additional_prefix,
+                prefix=additional_prefix+string[:len_lstrip],
             )
             additional_prefix = ''
             assert not node.previous_lines
             del fstring_stack[fstring_stack_index:]
-            return token, '', len(node.quote)
+            return token, '', len(node.quote) + len_lstrip
     return None, additional_prefix, 0
 
 
@@ -482,8 +484,20 @@ def tokenize_lines(lines, version_info, start_pos=(1, 0)):
                     yield fstring_end_token
                     continue
 
-            pseudomatch = pseudo_token.match(line, pos)
-            if not pseudomatch:                             # scan for tokens
+            # in an f-string, match until the end of the string
+            if fstring_stack:
+                string_line = line
+                for fstring_stack_node in fstring_stack:
+                    quote = fstring_stack_node.quote
+                    end_match = endpats[quote].match(line, pos)
+                    if end_match is not None:
+                        end_match_string = end_match.group(0)
+                        if len(end_match_string) - len(quote) + pos < len(string_line):
+                            string_line = line[:pos] + end_match_string[:-len(quote)]
+                pseudomatch = pseudo_token.match(string_line, pos)
+            else:
+                pseudomatch = pseudo_token.match(line, pos)
+            if not pseudomatch:  # scan for tokens
                 match = whitespace.match(line, pos)
                 if pos == 0:
                     for t in dedent_if_necessary(match.end()):
@@ -560,7 +574,12 @@ def tokenize_lines(lines, version_info, start_pos=(1, 0)):
                 new_line = True
             elif initial == '#':  # Comments
                 assert not token.endswith("\n")
-                additional_prefix = prefix + token
+                if fstring_stack and fstring_stack[-1].is_in_expr():
+                    # `#` is not allowed in f-string expressions
+                    yield PythonToken(ERRORTOKEN, initial, spos, prefix)
+                    pos = start + 1
+                else:
+                    additional_prefix = prefix + token
             elif token in triple_quoted:
                 endprog = endpats[token]
                 endmatch = endprog.match(line, pos)
@@ -616,10 +635,13 @@ def tokenize_lines(lines, version_info, start_pos=(1, 0)):
                     else:
                         if paren_level:
                             paren_level -= 1
-                elif token == ':' and fstring_stack \
+                elif token.startswith(':') and fstring_stack \
                         and fstring_stack[-1].parentheses_count \
                         - fstring_stack[-1].format_spec_count == 1:
+                    # `:` and `:=` both count
                     fstring_stack[-1].format_spec_count += 1
+                    token = ':'
+                    pos = start + 1
 
                 yield PythonToken(OP, token, spos, prefix)
 
diff --git a/test/test_tokenize.py b/test/test_tokenize.py
index bf703dc..3858145 100644
--- a/test/test_tokenize.py
+++ b/test/test_tokenize.py
@@ -385,8 +385,32 @@ def test_backslash():
             NAME, OP, FSTRING_START, FSTRING_STRING, OP, NAME, OP,
             FSTRING_STRING, OP, FSTRING_STRING, OP, NAME, OP, FSTRING_END, OP
         ]),
+        # issue #86, a string-like in an f-string expression
+        ('f"{ ""}"', [
+            FSTRING_START, OP, FSTRING_END, STRING
+        ]),
+        ('f"{ f""}"', [
+            FSTRING_START, OP, NAME, FSTRING_END, STRING
+        ]),
     ]
 )
 def test_fstring(code, types, version_ge_py36):
     actual_types = [t.type for t in _get_token_list(code, version_ge_py36)]
     assert types + [ENDMARKER] == actual_types
+
+
+@pytest.mark.parametrize(
+    ('code', 'types'), [
+        # issue #87, `:=` in the outest paratheses should be tokenized
+        # as a format spec marker and part of the format
+        ('f"{x:=10}"', [
+            FSTRING_START, OP, NAME, OP, FSTRING_STRING, OP, FSTRING_END
+        ]),
+        ('f"{(x:=10)}"', [
+            FSTRING_START, OP, OP, NAME, OP, NUMBER, OP, OP, FSTRING_END
+        ]),
+    ]
+)
+def test_fstring_assignment_expression(code, types, version_ge_py38):
+    actual_types = [t.type for t in _get_token_list(code, version_ge_py38)]
+    assert types + [ENDMARKER] == actual_types