diff --git a/gunicorn/http/message.py b/gunicorn/http/message.py
index 67fffd9e..4e1c2fd5 100644
--- a/gunicorn/http/message.py
+++ b/gunicorn/http/message.py
@@ -98,12 +98,16 @@ class Message(object):
                 raise InvalidHeader(curr)
             name, value = curr.split(":", 1)
             if self.cfg.strip_header_spaces:
-                name = name.rstrip(" \t").upper()
-            else:
-                name = name.upper()
+                name = name.rstrip(" \t")
             if not TOKEN_RE.fullmatch(name):
                 raise InvalidHeaderName(name)
 
+            # this is still a dangerous place to do this
+            #  but it is more correct than doing it before the pattern match:
+            # after we entered Unicode wonderland, 8bits could case-shift into ASCII:
+            # b"\xDF".decode("latin-1").upper().encode("ascii") == b"SS"
+            name = name.upper()
+
             value = [value.lstrip(" \t")]
 
             # Consume value continuation lines
diff --git a/tests/requests/invalid/nonascii_03.http b/tests/requests/invalid/nonascii_03.http
new file mode 100644
index 00000000..eda5d010
--- /dev/null
+++ b/tests/requests/invalid/nonascii_03.http
@@ -0,0 +1,5 @@
+GET /germans.. HTTP/1.1\r\n
+Content-Lengthß: 3\r\n
+Content-Length: 3\r\n
+\r\n
+ÄÄÄ
diff --git a/tests/requests/invalid/nonascii_03.py b/tests/requests/invalid/nonascii_03.py
new file mode 100644
index 00000000..d336fbc8
--- /dev/null
+++ b/tests/requests/invalid/nonascii_03.py
@@ -0,0 +1,5 @@
+from gunicorn.config import Config
+from gunicorn.http.errors import InvalidHeaderName
+
+cfg = Config()
+request = InvalidHeaderName