diff --git a/man/systemd.network.xml b/man/systemd.network.xml
index 02d56480b5..7cf9f2f6ed 100644
--- a/man/systemd.network.xml
+++ b/man/systemd.network.xml
@@ -1389,21 +1389,22 @@ IPv6Token=prefixstable:2002:da8:1::</programlisting></para>
         <varlistentry>
           <term><varname>InitialCongestionWindow=</varname></term>
           <listitem>
-            <para>The TCP initial congestion window is used during the start of a TCP connection. During the start of a TCP
-            session, when a client requests a resource, the server's initial congestion window determines how many data bytes
-            will be sent during the initial burst of data. Takes a size in bytes between 1 and 4294967295 (2^32 - 1). The usual
-            suffixes K, M, G are supported and are understood to the base of 1024. When unset, the kernel's default will be used.
-            </para>
+            <para>The TCP initial congestion window is used during the start of a TCP connection.
+            During the start of a TCP session, when a client requests a resource, the server's initial
+            congestion window determines how many packets will be sent during the initial burst of data
+            without waiting for acknowledgement. Takes a number between 1 and 1023. Note that 100 is
+            considered an extremely large value for this option. When unset, the kernel's default
+            (typically 10) will be used.</para>
           </listitem>
         </varlistentry>
         <varlistentry>
           <term><varname>InitialAdvertisedReceiveWindow=</varname></term>
           <listitem>
-            <para>The TCP initial advertised receive window is the amount of receive data (in bytes) that can initially be buffered at one time
-            on a connection. The sending host can send only that amount of data before waiting for an acknowledgment and window update
-            from the receiving host. Takes a size in bytes between 1 and 4294967295 (2^32 - 1). The usual suffixes K, M, G are supported
-            and are understood to the base of 1024. When unset, the kernel's default will be used.
-            </para>
+            <para>The TCP initial advertised receive window is the amount of receive data (in bytes)
+            that can initially be buffered at one time on a connection. The sending host can send only
+            that amount of data before waiting for an acknowledgment and window update from the
+            receiving host. Takes a number between 1 and 1023. Note that 100 is considered an extremely
+            large value for this option. When unset, the kernel's default will be used.</para>
           </listitem>
         </varlistentry>
         <varlistentry>
diff --git a/src/network/networkd-route.c b/src/network/networkd-route.c
index b82c4e7f79..2610b24c82 100644
--- a/src/network/networkd-route.c
+++ b/src/network/networkd-route.c
@@ -1465,7 +1465,7 @@ int config_parse_tcp_window(
 
         _cleanup_(route_free_or_set_invalidp) Route *n = NULL;
         Network *network = userdata;
-        uint64_t k;
+        uint32_t k;
         int r;
 
         assert(filename);
@@ -1483,13 +1483,13 @@ int config_parse_tcp_window(
                 return 0;
         }
 
-        r = parse_size(rvalue, 1024, &k);
+        r = safe_atou32(rvalue, &k);
         if (r < 0) {
                 log_syntax(unit, LOG_WARNING, filename, line, r,
                            "Could not parse TCP %s \"%s\", ignoring assignment: %m", lvalue, rvalue);
                 return 0;
         }
-        if (k > UINT32_MAX) {
+        if (k >= 1024) {
                 log_syntax(unit, LOG_WARNING, filename, line, 0,
                            "Specified TCP %s \"%s\" is too large, ignoring assignment: %m", lvalue, rvalue);
                 return 0;