diff --git a/CHANGES b/CHANGES
index 92b737589515a3c98a5b46f3c668f5fdbae6a167..bb05cb93f38f235071d5305a60c3a028de43ff4c 100644
--- a/CHANGES
+++ b/CHANGES
@@ -7,6 +7,11 @@
                                   Changelog
 
 
+Daniel Stenberg (7 Dec 2009)
+- Martin Storsjo made libcurl use the Expect: 100-continue header for posts
+  with unknown size. Previously it was only used for posts with a known size
+  larger than 1024 bytes.
+
 Daniel Stenberg (1 Dec 2009)
 - If the Expect: 100-continue header has been set by the application through
   curl_easy_setopt with CURLOPT_HTTPHEADER, the library should set
diff --git a/RELEASE-NOTES b/RELEASE-NOTES
index f6b38ce4500ef12d5c9e18ec7e69950c35042222..d916d438d687191c3aece1cf12f2d1fc5f952402 100644
--- a/RELEASE-NOTES
+++ b/RELEASE-NOTES
@@ -12,6 +12,7 @@ This release includes the following changes:
  o support SSL_FILETYPE_ENGINE for client certificate
  o curl-config can now show the arguments used when building curl
  o non-blocking TFTP
+ o send Expect: 100-continue for POSTs with unknown sizes
 
 This release includes the following bugfixes:
 
diff --git a/lib/http.c b/lib/http.c
index d67a001b26b53d10b190ee844fe9093721d4a0a3..6ac2d733102ce417138234f5b0a30842b8e8af2f 100644
--- a/lib/http.c
+++ b/lib/http.c
@@ -2815,7 +2815,7 @@ CURLcode Curl_http(struct connectdata *conn, bool *done)
       /* figure out the size of the postfields */
       postsize = (data->set.postfieldsize != -1)?
         data->set.postfieldsize:
-        (data->set.postfields? (curl_off_t)strlen(data->set.postfields):0);
+        (data->set.postfields? (curl_off_t)strlen(data->set.postfields):-1);
     }
     if(!data->req.upload_chunky) {
       /* We only set Content-Length and allow a custom Content-Length if
@@ -2849,7 +2849,7 @@ CURLcode Curl_http(struct connectdata *conn, bool *done)
       data->state.expect100header =
         Curl_compareheader(ptr, "Expect:", "100-continue");
     }
-    else if(postsize > TINY_INITIAL_POST_SIZE) {
+    else if(postsize > TINY_INITIAL_POST_SIZE || postsize < 0) {
       result = expect100(data, conn, req_buffer);
       if(result)
         return result;
diff --git a/tests/data/test510 b/tests/data/test510
index 360d6e96ee3d6e38f66d294e9a12d4b331069fac..8313f51c35ded8e9053be784329c99a222db880f 100644
--- a/tests/data/test510
+++ b/tests/data/test510
@@ -40,6 +40,7 @@ Host: %HOSTIP:%HTTPPORT
 Accept: */*
 Transfer-Encoding: chunked
 Content-Type: application/x-www-form-urlencoded
+Expect: 100-continue
 
 3
 one
diff --git a/tests/data/test565 b/tests/data/test565
index 896db4061bf512671f0bb81586bfb1d6782e7115..838941fefb927e834998990f74660a3e2da0998a 100644
--- a/tests/data/test565
+++ b/tests/data/test565
@@ -88,6 +88,7 @@ Host: 127.0.0.1:8990
 Accept: */*
 Transfer-Encoding: chunked
 Content-Type: application/x-www-form-urlencoded
+Expect: 100-continue
 
 3
 one