diff --git a/httpd.c b/httpd.c
index 5b4c80f4..5f341844 100644
--- a/httpd.c
+++ b/httpd.c
@@ -485,9 +485,16 @@ int http_response_content_type(httpd_request *r, uint16_t result, const char *wh
 
 int http_response_content_disposition(httpd_request *r, uint16_t result, const char *what, const char *type)
 {
-  DEBUGF(httpd, "%s Content-Disposition: %s %s", what, type);
+  DEBUGF(httpd, "%s Content-Disposition%s%s", what,
+	 type && type[0] ? ": " : "",
+	 type && type[0] ? type : " header"
+	);
   strbuf msg = strbuf_alloca(100);
-  strbuf_sprintf(msg, "%s Content-Disposition: %s", what, type);
+  strbuf_sprintf(msg, "%s Content-Disposition", what);
+  if (type && type[0])
+    strbuf_sprintf(msg, ": %s", type);
+  else
+    strbuf_puts(msg, " header");
   http_request_simple_response(&r->http, result, strbuf_str(msg)); // Unsupported Media Type
   return result;
 }
diff --git a/meshms_restful.c b/meshms_restful.c
index 25486757..7cce839a 100644
--- a/meshms_restful.c
+++ b/meshms_restful.c
@@ -609,6 +609,8 @@ static int send_mime_part_end(struct http_request *hr)
 static int send_mime_part_header(struct http_request *hr, const struct mime_part_headers *h)
 {
   httpd_request *r = (httpd_request *) hr;
+  if (!h->content_disposition.type[0])
+    return http_response_content_disposition(r, 415, "Missing", h->content_disposition.type);
   if (strcmp(h->content_disposition.type, "form-data") != 0)
     return http_response_content_disposition(r, 415, "Unsupported", h->content_disposition.type);
   if (strcmp(h->content_disposition.name, PART_MESSAGE) == 0) {
diff --git a/rhizome_direct_http.c b/rhizome_direct_http.c
index 5db64439..08dcaaee 100644
--- a/rhizome_direct_http.c
+++ b/rhizome_direct_http.c
@@ -309,6 +309,10 @@ static int rhizome_direct_process_mime_end(struct http_request *hr)
 static int rhizome_direct_process_mime_part_header(struct http_request *hr, const struct mime_part_headers *h)
 {
   httpd_request *r = (httpd_request *) hr;
+  if (!h->content_disposition.type[0])
+    return http_response_content_disposition(r, 415, "Missing", h->content_disposition.type);
+  if (strcmp(h->content_disposition.type, "form-data") != 0)
+    return http_response_content_disposition(r, 415, "Unsupported", h->content_disposition.type);
   if (   strcmp(h->content_disposition.name, PART_PAYLOAD) == 0
       || strcmp(h->content_disposition.name, PART_DATA) == 0
   ) {
diff --git a/rhizome_restful.c b/rhizome_restful.c
index 78c1c130..805c34ef 100644
--- a/rhizome_restful.c
+++ b/rhizome_restful.c
@@ -470,6 +470,8 @@ static int insert_make_manifest(httpd_request *r)
 static int insert_mime_part_header(struct http_request *hr, const struct mime_part_headers *h)
 {
   httpd_request *r = (httpd_request *) hr;
+  if (!h->content_disposition.type[0])
+    return http_response_content_disposition(r, 415, "Missing", h->content_disposition.type);
   if (strcmp(h->content_disposition.type, "form-data") != 0)
     return http_response_content_disposition(r, 415, "Unsupported", h->content_disposition.type);
   if (strcmp(h->content_disposition.name, PART_AUTHOR) == 0) {