diff --git a/.gitignore b/.gitignore
index 0ba244f6..fe6a1845 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,4 +7,3 @@ dist
 .coverage
 .tox
 .*cache
-htmlcov
\ No newline at end of file
diff --git a/prometheus_client/openmetrics/parser.py b/prometheus_client/openmetrics/parser.py
index 6230d962..a964abb6 100644
--- a/prometheus_client/openmetrics/parser.py
+++ b/prometheus_client/openmetrics/parser.py
@@ -3,6 +3,7 @@
 from __future__ import unicode_literals
 
 import math
+import sys
 
 from .. import core
 
@@ -112,11 +113,16 @@ def _parse_labels(it, text):
             elif char == '"':
                 if not core._METRIC_LABEL_NAME_RE.match(''.join(labelname)):
                     raise ValueError("Invalid line: " + text)
-                labels[''.join(labelname)] = ''.join(labelvalue)
+                utf8_str = ''.join(labelvalue)
+                try:
+                    utf8_str.encode('utf-8')
+                except UnicodeError:
+                    raise ValueError("Invalid line: " + text)
+                labels[''.join(labelname)] = utf8_str
                 labelname = []
                 labelvalue = []
                 state = 'endoflabelvalue'
-            else:
+            else:               
                 labelvalue.append(char)
         elif state == 'endoflabelvalue':
             if char == ',':
@@ -133,7 +139,7 @@ def _parse_labels(it, text):
                 labelvalue.append('\n')
             elif char == '"':
                 labelvalue.append('"')
-            else:
+            else:              
                 labelvalue.append('\\' + char)
         elif state == 'endoflabels':
             if char == ' ':
@@ -142,7 +148,6 @@ def _parse_labels(it, text):
                 raise ValueError("Invalid line: " + text)
     return labels
 
-
 def _parse_sample(text):
     name = []
     value = []
diff --git a/tests/openmetrics/test_parser.py b/tests/openmetrics/test_parser.py
index 9339530a..47e844f2 100644
--- a/tests/openmetrics/test_parser.py
+++ b/tests/openmetrics/test_parser.py
@@ -247,6 +247,23 @@ def test_labels_with_curly_braces(self):
         metric_family.add_metric(["bar", "b{a}z"], 1)
         self.assertEqual([metric_family], list(families))
 
+    def test_labels_with_invalid_utf8_values(self):
+        try:
+            if sys.version_info >= (3,):
+                inj = u'\uD802'
+            else:
+                inj = b'\xef'
+            str = '''# TYPE a counter
+# HELP a help
+a_total{foo="'''+inj+'''",bar="baz"} 1
+# EOF
+'''
+            families = text_string_to_metric_families(str)
+            for f in families: pass
+            assert False
+        except ValueError:
+            assert True
+
     def test_empty_help(self):
         families = text_string_to_metric_families("""# TYPE a counter
 # HELP a