diff --git a/lib/ota/src/update_parser.h b/lib/ota/src/update_parser.h
index 0c6114c..128a03c 100644
--- a/lib/ota/src/update_parser.h
+++ b/lib/ota/src/update_parser.h
@@ -50,6 +50,8 @@ class UpdateParser {
 
     void feed(const uint8_t* data, size_t len);
     bool end();  // no more data: true if the update was installed
+    // The whole image the header announced has arrived (the sender need not close the connection).
+    bool complete() const { return state_ == State::Image && received_ == imageSize_; }
 
     State state() const { return state_; }
     const std::string& error() const { return error_; }
diff --git a/scripts/ota_push.py b/scripts/ota_push.py
index aaf06a3..b035e8b 100755
--- a/scripts/ota_push.py
+++ b/scripts/ota_push.py
@@ -17,16 +17,29 @@ def main():
     data = open(path, "rb").read()
     with socket.create_connection((host, PORT), timeout=15) as s:
         s.settimeout(60)
-        sent = 0
+        sent, last = 0, -1
         while sent < len(data):
             chunk = data[sent:sent + 4096]
             s.sendall(chunk)
             sent += len(chunk)
-            print(f"\rsending {sent * 100 // len(data):3d}%", end="", flush=True)
-        s.shutdown(socket.SHUT_WR)  # end of file: the device checks it and answers
+            pct = sent * 100 // len(data)
+            if pct != last:
+                print(f"\rsending {pct:3d}%", end="", flush=True)
+                last = pct
+        # The header announces the image size, so current firmware answers once it has it all.
+        # Firmware from before that change only knows the file ended when we half-close.
         reply = b""
-        while not reply.endswith(b"\n"):
-            part = s.recv(256)
+        s.settimeout(3)
+        try:
+            reply = s.recv(256)
+        except socket.timeout:
+            s.shutdown(socket.SHUT_WR)
+            s.settimeout(60)
+        while reply == b"" or not reply.endswith(b"\n"):
+            try:
+                part = s.recv(256)
+            except socket.timeout:
+                break
             if not part:
                 break
             reply += part
diff --git a/src/services/update_service.cpp b/src/services/update_service.cpp
index 11fb45e..44c498a 100644
--- a/src/services/update_service.cpp
+++ b/src/services/update_service.cpp
@@ -132,6 +132,10 @@ void UpdateService::install(UpdateSource& source, const char* via) {
         if (incoming_.empty() && parser.state() == UpdateParser::State::Image) incoming_ = parser.version();
         percent_ = parser.percent();
         if (parser.state() == UpdateParser::State::Failed) break;
+        if (parser.complete()) {  // all announced bytes are here: answer while the connection is open
+            ok = parser.end();
+            break;
+        }
     }
     if (!ok && parser.error().empty()) parser.end();  // e.g. a stall: abort the slot
 
diff --git a/test/test_ota/test_ota.cpp b/test/test_ota/test_ota.cpp
index 27f7589..c8af9a8 100644
--- a/test/test_ota/test_ota.cpp
+++ b/test/test_ota/test_ota.cpp
@@ -138,6 +138,18 @@ void test_progress_counts_image_bytes() {
     TEST_ASSERT_EQUAL(25, p.percent());
 }
 
+void test_complete_once_the_declared_image_size_has_arrived() {
+    FakeVerifier v;
+    MemorySink sink;
+    auto file = makeFile("v0.3.0", image(300));
+    UpdateParser p(v, sink, 100000, "v0.2.1");
+    p.feed(file.data(), file.size() - 1);
+    TEST_ASSERT_FALSE(p.complete());
+    p.feed(file.data() + file.size() - 1, 1);
+    TEST_ASSERT_TRUE(p.complete());
+    TEST_ASSERT_TRUE(p.end());
+}
+
 void test_not_an_update_file_is_refused_before_writing() {
     FakeVerifier v;
     MemorySink sink;
@@ -273,6 +285,7 @@ int main() {
     RUN_TEST(test_valid_file_in_one_chunk_is_installed);
     RUN_TEST(test_valid_file_byte_by_byte);
     RUN_TEST(test_progress_counts_image_bytes);
+    RUN_TEST(test_complete_once_the_declared_image_size_has_arrived);
     RUN_TEST(test_not_an_update_file_is_refused_before_writing);
     RUN_TEST(test_bad_signature_is_refused_before_writing);
     RUN_TEST(test_tampered_version_breaks_the_signature);