diff --git a/src/edit.c b/src/edit.c
index 04a17eb..0bcc9db 100644
--- a/src/edit.c
+++ b/src/edit.c
@@ -58,6 +58,10 @@
 };
 
 static char e_hitend[] = N_("Hit end of paragraph");
+#ifdef FEAT_COMPL_FUNC
+static char e_complwin[] = N_("E839: Completion function changed window");
+static char e_compldel[] = N_("E840: Completion function deleted text");
+#endif
 
 /*
  * Structure used to store one match for insert completion.
@@ -3833,6 +3837,8 @@
     char_u	*args[2];
     char_u	*funcname;
     pos_T	pos;
+    win_T	*curwin_save;
+    buf_T	*curbuf_save;
 
     funcname = (type == CTRL_X_FUNCTION) ? curbuf->b_p_cfu : curbuf->b_p_ofu;
     if (*funcname == NUL)
@@ -3843,13 +3849,27 @@
     args[1] = base;
 
     pos = curwin->w_cursor;
+    curwin_save = curwin;
+    curbuf_save = curbuf;
     matchlist = call_func_retlist(funcname, 2, args, FALSE);
+    if (curwin_save != curwin || curbuf_save != curbuf)
+    {
+	EMSG(_(e_complwin));
+	goto theend;
+    }
     curwin->w_cursor = pos;	/* restore the cursor position */
-    if (matchlist == NULL)
-	return;
+    check_cursor();
+    if (!equalpos(curwin->w_cursor, pos))
+    {
+	EMSG(_(e_compldel));
+	goto theend;
+    }
+    if (matchlist != NULL)
+	ins_compl_add_list(matchlist);
 
-    ins_compl_add_list(matchlist);
-    list_unref(matchlist);
+theend:
+    if (matchlist != NULL)
+	list_unref(matchlist);
 }
 #endif /* FEAT_COMPL_FUNC */
 
@@ -4994,6 +5014,8 @@
 	    int		col;
 	    char_u	*funcname;
 	    pos_T	pos;
+	    win_T	*curwin_save;
+	    buf_T	*curbuf_save;
 
 	    /* Call 'completefunc' or 'omnifunc' and get pattern length as a
 	     * string */
@@ -5009,8 +5031,21 @@
 	    args[0] = (char_u *)"1";
 	    args[1] = NULL;
 	    pos = curwin->w_cursor;
+	    curwin_save = curwin;
+	    curbuf_save = curbuf;
 	    col = call_func_retnr(funcname, 2, args, FALSE);
+	    if (curwin_save != curwin || curbuf_save != curbuf)
+	    {
+		EMSG(_(e_complwin));
+		return FAIL;
+	    }
 	    curwin->w_cursor = pos;	/* restore the cursor position */
+	    check_cursor();
+	    if (!equalpos(curwin->w_cursor, pos))
+	    {
+		EMSG(_(e_compldel));
+		return FAIL;
+	    }
 
 	    if (col < 0)
 		col = curs_col;
diff --git a/src/testdir/Make_amiga.mak b/src/testdir/Make_amiga.mak
index 2e6ad69..c4a6c7f 100644
--- a/src/testdir/Make_amiga.mak
+++ b/src/testdir/Make_amiga.mak
@@ -27,7 +27,8 @@
 		test56.out test57.out test58.out test59.out test60.out \
 		test61.out test62.out test63.out test64.out test65.out \
 		test66.out test67.out test68.out test69.out test70.out \
-		test71.out test72.out test73.out test74.out test75.out
+		test71.out test72.out test73.out test74.out test75.out \
+		test76.out
 
 .SUFFIXES: .in .out
 
@@ -122,3 +123,4 @@
 test73.out: test73.in
 test74.out: test74.in
 test75.out: test75.in
+test76.out: test76.in
diff --git a/src/testdir/Make_dos.mak b/src/testdir/Make_dos.mak
index 87de055..3395c52 100644
--- a/src/testdir/Make_dos.mak
+++ b/src/testdir/Make_dos.mak
@@ -28,7 +28,7 @@
 		test37.out test38.out test39.out test40.out test41.out \
 		test42.out test52.out test65.out test66.out test67.out \
 		test68.out test69.out test71.out test72.out test73.out \
-		test74.out test75.out
+		test74.out test75.out test76.out
 
 SCRIPTS32 =	test50.out test70.out
 
diff --git a/src/testdir/Make_ming.mak b/src/testdir/Make_ming.mak
index 1d29e52..1d89dff 100644
--- a/src/testdir/Make_ming.mak
+++ b/src/testdir/Make_ming.mak
@@ -48,7 +48,7 @@
 		test37.out test38.out test39.out test40.out test41.out \
 		test42.out test52.out test65.out test66.out test67.out \
 		test68.out test69.out test71.out test72.out test73.out \
-		test74.out test75.out
+		test74.out test75.out test76.out
 
 SCRIPTS32 =	test50.out test70.out
 
diff --git a/src/testdir/Make_os2.mak b/src/testdir/Make_os2.mak
index f05c679..361e693 100644
--- a/src/testdir/Make_os2.mak
+++ b/src/testdir/Make_os2.mak
@@ -27,7 +27,8 @@
 		test56.out test57.out test58.out test59.out test60.out \
 		test61.out test62.out test63.out test64.out test65.out \
 		test66.out test67.out test68.out test69.out test70.out \
-		test71.out test72.out test73.out test74.out test75.out
+		test71.out test72.out test73.out test74.out test75.out \
+		test76.out
 
 .SUFFIXES: .in .out
 
diff --git a/src/testdir/Make_vms.mms b/src/testdir/Make_vms.mms
index 7806540..5ddb1d8 100644
--- a/src/testdir/Make_vms.mms
+++ b/src/testdir/Make_vms.mms
@@ -4,7 +4,7 @@
 # Authors:	Zoltan Arpadffy, <arpadffy@polarhome.com>
 #		Sandor Kopanyi,  <sandor.kopanyi@mailbox.hu>
 #
-# Last change:  2010 Oct 20
+# Last change:  2010 Nov 10
 #
 # This has been tested on VMS 6.2 to 8.3 on DEC Alpha, VAX and IA64.
 # Edit the lines in the Configuration section below to select.
@@ -74,7 +74,7 @@
 	 test56.out test57.out test60.out \
 	 test61.out test62.out test63.out test64.out test65.out \
 	 test66.out test67.out test68.out test69.out \
-	 test71.out test72.out test74.out test75.out
+	 test71.out test72.out test74.out test75.out test76.out
 
 # Known problems:
 # Test 30: a problem around mac format - unknown reason
diff --git a/src/testdir/Makefile b/src/testdir/Makefile
index 25591a1..833a82a 100644
--- a/src/testdir/Makefile
+++ b/src/testdir/Makefile
@@ -25,7 +25,7 @@
 		test59.out test60.out test61.out test62.out test63.out \
 		test64.out test65.out test66.out test67.out test68.out \
 		test69.out test70.out test71.out test72.out test73.out \
-		test74.out test75.out
+		test74.out test75.out test76.out
 
 SCRIPTS_GUI = test16.out
 
diff --git a/src/version.c b/src/version.c
index 24992e7..f9609aa 100644
--- a/src/version.c
+++ b/src/version.c
@@ -715,6 +715,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    52,
+/**/
     51,
 /**/
     50,