diff --git a/akka-http-core/src/main/scala/akka/http/impl/engine/parsing/BodyPartParser.scala b/akka-http-core/src/main/scala/akka/http/impl/engine/parsing/BodyPartParser.scala
index bf8578e53e..7086f937a9 100644
--- a/akka-http-core/src/main/scala/akka/http/impl/engine/parsing/BodyPartParser.scala
+++ b/akka-http-core/src/main/scala/akka/http/impl/engine/parsing/BodyPartParser.scala
@@ -98,7 +98,7 @@ private[http] final class BodyPartParser(defaultContentType: ContentType,
         else parsePreamble(input, 0)
       } else parsePreamble(input, 0)
     } catch {
-      case NotEnoughDataException ⇒ continue((input, _) ⇒ tryParseInitialBoundary(input))
+      case NotEnoughDataException ⇒ continue(input, 0)((newInput, _) ⇒ tryParseInitialBoundary(newInput))
     }
 
   def parsePreamble(input: ByteString, offset: Int): StateResult =
diff --git a/akka-http-tests/src/test/scala/akka/http/scaladsl/unmarshalling/MultipartUnmarshallersSpec.scala b/akka-http-tests/src/test/scala/akka/http/scaladsl/unmarshalling/MultipartUnmarshallersSpec.scala
index 306571d2f7..505821ecfb 100644
--- a/akka-http-tests/src/test/scala/akka/http/scaladsl/unmarshalling/MultipartUnmarshallersSpec.scala
+++ b/akka-http-tests/src/test/scala/akka/http/scaladsl/unmarshalling/MultipartUnmarshallersSpec.scala
@@ -49,7 +49,7 @@ class MultipartUnmarshallersSpec extends FreeSpec with Matchers with BeforeAndAf
             |--XYZABC--""".stripMarginWithNewline("\r\n"))).to[Multipart.General] should haveParts(
           Multipart.General.BodyPart.Strict(HttpEntity.empty(MediaTypes.`text/xml`), List(Age(12))))
       }
-      "an implicitly typed part (without headers)" in {
+      "an implicitly typed part (without headers) (Strict)" in {
         Unmarshal(HttpEntity(`multipart/mixed` withBoundary "XYZABC",
           """--XYZABC
             |
@@ -57,6 +57,16 @@ class MultipartUnmarshallersSpec extends FreeSpec with Matchers with BeforeAndAf
             |--XYZABC--""".stripMarginWithNewline("\r\n"))).to[Multipart.General] should haveParts(
           Multipart.General.BodyPart.Strict(HttpEntity(ContentTypes.`text/plain(UTF-8)`, "Perfectly fine part content.")))
       }
+      "an implicitly typed part (without headers) (Default)" in {
+        val content = """--XYZABC
+                        |
+                        |Perfectly fine part content.
+                        |--XYZABC--""".stripMarginWithNewline("\r\n")
+        val byteStrings = content.map(c ⇒ ByteString(c.toString)) // one-char ByteStrings
+        Unmarshal(HttpEntity.Default(`multipart/mixed` withBoundary "XYZABC", content.length, Source(byteStrings)))
+          .to[Multipart.General] should haveParts(
+            Multipart.General.BodyPart.Strict(HttpEntity(ContentTypes.`text/plain(UTF-8)`, "Perfectly fine part content.")))
+      }
       "one non-empty form-data part" in {
         Unmarshal(HttpEntity(`multipart/form-data` withBoundary "-",
           """---