diff --git a/botocore/eventstream.py b/botocore/eventstream.py
index b7999a6e50..1f725ff412 100644
--- a/botocore/eventstream.py
+++ b/botocore/eventstream.py
@@ -466,9 +466,9 @@ def _parse_prelude(self):
         prelude_bytes = self._data[:_PRELUDE_LENGTH]
         raw_prelude, _ = DecodeUtils.unpack_prelude(prelude_bytes)
         prelude = MessagePrelude(*raw_prelude)
-        self._validate_prelude(prelude)
         # The minus 4 removes the prelude crc from the bytes to be checked
         _validate_checksum(prelude_bytes[: _PRELUDE_LENGTH - 4], prelude.crc)
+        self._validate_prelude(prelude)
         return prelude
 
     def _parse_headers(self):
diff --git a/tests/unit/test_eventstream.py b/tests/unit/test_eventstream.py
index a683e37e7f..c88acc1b75 100644
--- a/tests/unit/test_eventstream.py
+++ b/tests/unit/test_eventstream.py
@@ -218,7 +218,7 @@
         b"\x00\x00\x00=\xff\x00\x01\x02\x07\xfd\x83\x96\x0ccontent-type\x07\x00"
         b"\x10application/json{'foo':'bar'}\x8d\x9c\x08\xb1"
     ),
-    InvalidHeadersLength,
+    ChecksumMismatch,
 )
 
 CORRUPTED_HEADERS = (
@@ -231,7 +231,7 @@
 
 CORRUPTED_LENGTH = (
     b"\x01\x00\x00\x1d\x00\x00\x00\x00\xfdR\x8cZ{'foo':'bar'}\xc3e96",
-    InvalidPayloadLength,
+    ChecksumMismatch,
 )
 
 CORRUPTED_PAYLOAD = (
@@ -247,6 +247,31 @@
     DuplicateHeader,
 )
 
+# In contrast to the CORRUPTED_HEADERS case, this message is otherwise
+# well-formed - the checksums match.
+INVALID_HEADERS_LENGTH = (
+    (
+        b"\x00\x00\x00\x3d"  # total length
+        b"\xff\x00\x01\x02"  # headers length
+        b"\x15\x83\xf5\xc2"  # prelude crc
+        b"\x0ccontent-type\x07\x00\x10application/json"  # headers
+        b"{'foo':'bar'}"  # payload
+        b"\x2f\x37\x7f\x5d"  # message crc
+    ),
+    InvalidHeadersLength,
+)
+
+# In contrast to the CORRUPTED_PAYLOAD case, this message is otherwise
+# well-formed - the checksums match.
+INVALID_PAYLOAD_LENGTH = (
+    b"\x01\x00\x00\x11"  # total length
+    + b"\x00\x00\x00\x00"  # headers length
+    + b"\xf4\x08\x61\xc5"  # prelude crc
+    + b"0" * (16 * 1024**2 + 1)  # payload
+    + b"\x2a\xb4\xc5\xa5",  # message crc
+    InvalidPayloadLength,
+)
+
 # Tuples of encoded messages and their expected exception
 NEGATIVE_CASES = [
     CORRUPTED_LENGTH,
@@ -254,6 +279,8 @@
     CORRUPTED_HEADERS,
     CORRUPTED_HEADER_LENGTH,
     DUPLICATE_HEADER,
+    INVALID_HEADERS_LENGTH,
+    INVALID_PAYLOAD_LENGTH,
 ]