diff --git a/src/datetime/tests.rs b/src/datetime/tests.rs
index 407f17e8af..361b034d68 100644
--- a/src/datetime/tests.rs
+++ b/src/datetime/tests.rs
@@ -805,6 +805,8 @@ fn test_parse_datetime_utc() {
         "2001-02-03T04:05:06+0000",
         "2001-02-03T04:05:06-00:00",
         "2001-02-03T04:05:06-01:00",
+        "2012-12-12 12:12:12Z",
+        "2012-12-12t12:12:12Z",
         "2012-12-12T12:12:12Z",
         "2012 -12-12T12:12:12Z",
         "2012  -12-12T12:12:12Z",
@@ -871,7 +873,6 @@ fn test_parse_datetime_utc() {
         "2012-12-12T12:61:12Z",     // invalid minute
         "2012-12-12T12:12:62Z",     // invalid second
         "2012-12-12 T12:12:12Z",    // space after date
-        "2012-12-12t12:12:12Z",     // wrong divider 't'
         "2012-12-12T12:12:12ZZ",    // trailing literal 'Z'
         "+802701-12-12T12:12:12Z",  // invalid year (out of bounds)
         "+ 2012-12-12T12:12:12Z",   // invalid space before year
diff --git a/src/format/parse.rs b/src/format/parse.rs
index 210a554c92..b3099672aa 100644
--- a/src/format/parse.rs
+++ b/src/format/parse.rs
@@ -567,10 +567,14 @@ fn parse_rfc3339_relaxed<'a>(parsed: &mut Parsed, mut s: &'a str) -> ParseResult
         Err((_s, e)) => return Err(e),
         Ok(_) => return Err(NOT_ENOUGH),
     };
-    if !(s.starts_with('T') || s.starts_with(' ')) {
-        return Err(INVALID);
-    }
-    match parse_internal(parsed, &s[1..], TIME_ITEMS.iter()) {
+
+    s = match s.as_bytes().first() {
+        Some(&b't' | &b'T' | &b' ') => &s[1..],
+        Some(_) => return Err(INVALID),
+        None => return Err(TOO_SHORT),
+    };
+
+    match parse_internal(parsed, s, TIME_ITEMS.iter()) {
         Err((s, e)) if e.0 == ParseErrorKind::TooLong => Ok((s, ())),
         Err((_s, e)) => Err(e),
         Ok(s) => Ok((s, ())),