diff --git a/NEWS.md b/NEWS.md
index ae13e03..afa3de7 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,7 @@
 # httptest2 1.1.0.9000
 
+* `build_mock_url()` now works with multipart body request containing character strings or raw data (#40, @jmaspons)
+
 # httptest2 1.1.0
 
 * `request` is now removed when saving `httr2_response` objects. In earlier versions of `httr2`, requests were not included in responses, but in httr2 1.0.0, [they were added](https://github.com/r-lib/httr2/pull/359) in order to improve error messages. *If you recorded any responses with httr2 >= 1.0 and httptest2 prior to this version, you may have leaked auth secrets: this would happen if your requests included auth information (as in an `Authentication` header), and the response was saved in a .R file, not simplified to .json or other response-body-only formats. Please inspect your recorded responses and invalidate any tokens that were exposed.*
@@ -38,4 +40,4 @@ Changes to function signatures:
 
 * The `path` argument to `capture_requests()` and `start_capturing()` has been removed; instead set the mock path explicitly with `.mockPaths()` or use `with_mock_dir()`.
 * Internal function `save_response()` requires a `file` path argument because `httr2_response` objects do not contain their `request`, which is needed to construct the mock file path
-* Internal function `build_mock_url()` no longer accepts a string URL as an input; it only accepts `request` objects
\ No newline at end of file
+* Internal function `build_mock_url()` no longer accepts a string URL as an input; it only accepts `request` objects
diff --git a/R/build-mock-url.R b/R/build-mock-url.R
index 74bd752..9c9315f 100644
--- a/R/build-mock-url.R
+++ b/R/build-mock-url.R
@@ -79,9 +79,11 @@ get_string_request_body <- function(req) {
         if (inherits(x, "form_file")) {
           # hash the file contents
           paste("File:", digest(x$path, serialize = FALSE, file = TRUE))
-        } else {
-          # assume form_data
+        } else if (inherits(x, "form_data")) {
           rawToChar(x$value)
+        } else {
+          # assume character string or raw
+          x
         }
       })
       b <- paste(c(
diff --git a/tests/testthat/test-capture-requests.R b/tests/testthat/test-capture-requests.R
index 94a38dd..2e1a6f9 100644
--- a/tests/testthat/test-capture-requests.R
+++ b/tests/testthat/test-capture-requests.R
@@ -1,6 +1,8 @@
 d <- tempfile()
 dl_file <- tempfile()
 webp_file <- tempfile()
+file_path <- tempfile()
+cat(letters[1:6], file = file_path)
 
 # The webfake URL will be something like 127.0.0.1:port, and port may vary
 # so the mock paths will be different every time it runs
@@ -31,6 +33,15 @@ test_that("We can record a series of requests (a few ways)", {
       req_perform(path = webp_file)
     r8 <<- request(httpbin$url("/status/202")) %>% req_perform()
     r9 <<- request(httpbin$url("/status/200")) %>% req_perform()
+    r10 <<- request(httpbin$url("/post")) %>%
+      req_body_multipart(
+        file = curl::form_file(file_path),
+        string = "some text",
+        form_data = curl::form_data("form data"),
+        raw_data = charToRaw("raw data")
+      ) %>%
+      req_method("POST") %>%
+      req_perform()
     stop_capturing()
   })
 
@@ -41,6 +52,7 @@ test_that("We can record a series of requests (a few ways)", {
     "httpbin.org/get.json",
     "httpbin.org/image/webp.R", # Not a simplifiable format, so .R
     "httpbin.org/image/webp.R-FILE", # The `write_disk` location
+    "httpbin.org/post-48db67-POST.json",
     "httpbin.org/put-PUT.json", # Not a GET, but returns 200
     "httpbin.org/response-headers-ac4928.json",
     "httpbin.org/status/200.txt", # empty 200 response "text/plain", so .txt
@@ -94,6 +106,15 @@ test_that("We can then load the mocks it stores", {
         req_perform(path = mock_webp_file)
       m8 <- request(httpbin$url("/status/202")) %>% req_perform()
       m9 <- request(httpbin$url("/status/200")) %>% req_perform()
+      m10 <- request(httpbin$url("/post")) %>%
+        req_body_multipart(
+          file = curl::form_file(file_path),
+          string = "some text",
+          form_data = curl::form_data("form data"),
+          raw_data = charToRaw("raw data")
+        ) %>%
+        req_method("POST") %>%
+        req_perform()
     })
   })
   expect_identical(resp_body_json(m1), resp_body_json(r1))
@@ -114,6 +135,7 @@ test_that("We can then load the mocks it stores", {
   expect_equal(resp_status(m9), 200)
   expect_equal(resp_content_type(m9), "text/plain")
   expect_false(resp_has_body(m9))
+  expect_identical(resp_body_json(m10), resp_body_json(r10))
 })
 
 test_that("write_disk mocks can be reloaded even if the mock directory moves", {
diff --git a/tests/testthat/test-mock-api.R b/tests/testthat/test-mock-api.R
index beea45c..4a10434 100644
--- a/tests/testthat/test-mock-api.R
+++ b/tests/testthat/test-mock-api.R
@@ -175,13 +175,17 @@ with_mock_api({
       r %>%
         req_body_multipart(
           a = curl::form_file(file_to_upload),
-          b = curl::form_data("strings")
+          b = curl::form_data("strings"),
+          c = "some text",
+          d = charToRaw("raw data")
         ) %>%
         req_perform(),
       "http://httpbin.not/post",
       "Multipart form:
   a = File: ae2b1fca515949e5d54fb22b8ed95575
-  b = strings"
+  b = strings
+  c = some text
+  d = as.raw(c(0x72, 0x61, 0x77, 0x20, 0x64, 0x61, 0x74, 0x61))"
     )
   })