diff --git a/R/parse-body.R b/R/parse-body.R
index 4e8d3ea58..a5198700f 100644
--- a/R/parse-body.R
+++ b/R/parse-body.R
@@ -192,8 +192,11 @@ parser_multi <- function() {
     toparse <- parse_multipart(value, boundary)
     # content-type detection
     lapply(toparse, function(x) {
-      if (!is.null(x$filename)) {
-        x$content_type <- getContentType(tools::file_ext(x$filename))
+      if (is.null(x$content_type) || isTRUE(x$content_type == "application/octet-stream")) {
+        if (!is.null(x$filename)) {
+          # Guess content-type from file extension
+          x$content_type <- getContentType(tools::file_ext(x$filename))
+        }
       }
       parseRaw(x)
     })
diff --git a/tests/testthat/files/.gitattributes b/tests/testthat/files/.gitattributes
new file mode 100644
index 000000000..291377b6b
--- /dev/null
+++ b/tests/testthat/files/.gitattributes
@@ -0,0 +1 @@
+*.bin binary
diff --git a/tests/testthat/files/multipart-ctype.bin b/tests/testthat/files/multipart-ctype.bin
new file mode 100644
index 000000000..a76b50942
--- /dev/null
+++ b/tests/testthat/files/multipart-ctype.bin
@@ -0,0 +1,18 @@
+-----------------------------90908882332870323642673870272
+Content-Disposition: form-data; name="file"; filename="sample.tsv"
+Content-Type: text/tab-separated-values
+
+x	y	z
+0.118413259	0.708780115	0.220421733
+0.7442446	0.539953502	0.02358455
+0.452216508	0.434335382	0.290591105
+0.177870351	0.329585854	0.867134948
+0.328333594	0.564684198	0.455520456
+0.680873191	0.57619709	0.015501929
+0.87209177	0.4487502	0.008787638
+0.50966466	0.958683547	0.251500478
+0.937677985	0.457557468	0.19860169
+0.352366596	0.49283506	0.161614863
+0.370598572	0.366986682	0.15623896
+
+-----------------------------90908882332870323642673870272--
diff --git a/tests/testthat/test-postbody.R b/tests/testthat/test-postbody.R
index 1cce315b9..4ad6c5f72 100644
--- a/tests/testthat/test-postbody.R
+++ b/tests/testthat/test-postbody.R
@@ -67,3 +67,10 @@ test_that("Test multipart parser", {
   expect_equal(attr(parsed_body[["img1"]], "filename"), "avatar2-small.png")
   expect_equal(parsed_body[["json"]], list(a=2,b=4,c=list(w=3,t=5)))
 })
+
+test_that("Test multipart respect content-type", {
+  bin_file <- test_path("files/multipart-ctype.bin")
+  body <- readBin(bin_file, what = "raw", n = file.info(bin_file)$size)
+  parsed_body <- parseBody(body, "multipart/form-data; boundary=---------------------------90908882332870323642673870272")
+  expect_equal(class(parsed_body$file), "character")
+})