diff --git a/docs/src/tcp.rst b/docs/src/tcp.rst
index cccc86bb..f351214f 100644
--- a/docs/src/tcp.rst
+++ b/docs/src/tcp.rst
@@ -65,6 +65,10 @@ API
     at the end of this procedure, then the handle is destroyed with a
     ``UV_ETIMEDOUT`` error passed to the corresponding callback.
 
+    If `delay` is less than 1 then ``UV_EINVAL`` is returned.
+
+    .. versionchanged:: 1.49.0 If `delay` is less than 1 then ``UV_EINVAL``` is returned.
+
 .. c:function:: int uv_tcp_simultaneous_accepts(uv_tcp_t* handle, int enable)
 
     Enable / disable simultaneous asynchronous accept requests that are
diff --git a/src/unix/tcp.c b/src/unix/tcp.c
index 56f2c04b..f3bef304 100644
--- a/src/unix/tcp.c
+++ b/src/unix/tcp.c
@@ -467,8 +467,8 @@ int uv__tcp_keepalive(int fd, int on, unsigned int delay) {
   if (!on)
     return 0;
 
-  if (delay == 0)
-    return -1;
+  if (delay < 1)
+    return UV_EINVAL;
 
 #ifdef __sun
   /* The implementation of TCP keep-alive on Solaris/SmartOS is a bit unusual
diff --git a/src/win/tcp.c b/src/win/tcp.c
index 187f36e2..c2efc481 100644
--- a/src/win/tcp.c
+++ b/src/win/tcp.c
@@ -58,11 +58,17 @@ static int uv__tcp_keepalive(uv_tcp_t* handle, SOCKET socket, int enable, unsign
     return WSAGetLastError();
   }
 
-  if (enable && setsockopt(socket,
-                           IPPROTO_TCP,
-                           TCP_KEEPALIVE,
-                           (const char*)&delay,
-                           sizeof delay) == -1) {
+  if (!enable)
+    return 0;
+
+  if (delay < 1)
+    return UV_EINVAL;
+
+  if (setsockopt(socket,
+                 IPPROTO_TCP,
+                 TCP_KEEPALIVE,
+                 (const char*)&delay,
+                 sizeof delay) == -1) {
     return WSAGetLastError();
   }
 
diff --git a/test/test-tcp-flags.c b/test/test-tcp-flags.c
index 30178d70..16218a27 100644
--- a/test/test-tcp-flags.c
+++ b/test/test-tcp-flags.c
@@ -33,7 +33,8 @@ TEST_IMPL(tcp_flags) {
 
   loop = uv_default_loop();
 
-  r = uv_tcp_init(loop, &handle);
+  /* Use _ex to make sure the socket is created. */
+  r = uv_tcp_init_ex(loop, &handle, AF_INET);
   ASSERT_OK(r);
 
   r = uv_tcp_nodelay(&handle, 1);
@@ -42,6 +43,12 @@ TEST_IMPL(tcp_flags) {
   r = uv_tcp_keepalive(&handle, 1, 60);
   ASSERT_OK(r);
 
+  r = uv_tcp_keepalive(&handle, 0, 0);
+  ASSERT_OK(r);
+
+  r = uv_tcp_keepalive(&handle, 1, 0);
+  ASSERT_EQ(r, UV_EINVAL);
+
   uv_close((uv_handle_t*)&handle, NULL);
 
   r = uv_run(loop, UV_RUN_DEFAULT);