diff --git a/winsup/cygwin/fhandler.h b/winsup/cygwin/fhandler.h
index bed698f86..ec222aef5 100644
--- a/winsup/cygwin/fhandler.h
+++ b/winsup/cygwin/fhandler.h
@@ -2213,14 +2213,7 @@ class fhandler_pty_slave: public fhandler_pty_common
   void set_switch_to_pcon (int fd);
   void reset_switch_to_pcon (void);
   void push_to_pcon_screenbuffer (const char *ptr, size_t len);
-  void mask_switch_to_pcon_in (bool mask)
-  {
-    if (!mask && get_ttyp ()->pcon_pid &&
-	get_ttyp ()->pcon_pid != myself->pid &&
-	!!pinfo (get_ttyp ()->pcon_pid))
-      return;
-    get_ttyp ()->mask_switch_to_pcon_in = mask;
-  }
+  void mask_switch_to_pcon_in (bool mask);
   void fixup_after_attach (bool native_maybe, int fd);
   bool is_line_input (void)
   {
diff --git a/winsup/cygwin/fhandler_tty.cc b/winsup/cygwin/fhandler_tty.cc
index 181bed5a9..a92bcfc40 100644
--- a/winsup/cygwin/fhandler_tty.cc
+++ b/winsup/cygwin/fhandler_tty.cc
@@ -1395,6 +1395,16 @@ fhandler_pty_slave::write (const void *ptr, size_t len)
   return towrite;
 }
 
+void
+fhandler_pty_slave::mask_switch_to_pcon_in (bool mask)
+{
+  if (!mask && get_ttyp ()->pcon_pid &&
+      get_ttyp ()->pcon_pid != myself->pid &&
+      !!pinfo (get_ttyp ()->pcon_pid))
+    return;
+  get_ttyp ()->mask_switch_to_pcon_in = mask;
+}
+
 bool
 fhandler_pty_common::to_be_read_from_pcon (void)
 {