Index: generic/ttk/ttkManager.c
==================================================================
--- generic/ttk/ttkManager.c
+++ generic/ttk/ttkManager.c
@@ -432,30 +432,39 @@
 	if (mgr->content[index]->window == window)
 	    return index;
     return -1;
 }
 
-/* ++ Ttk_GetContentIndexFromObj(interp, mgr, objPtr, indexPtr) --
+/* ++ Ttk_GetContentIndexFromObj(interp, mgr, objPtr, lastOK, indexPtr) --
  * 	Return the index of the content window specified by objPtr.
  * 	Content windows may be specified as an integer index or
  * 	as the name of the managed window.
+ *
+ *  The parameter lastOK should be non-0 if the resolved index can be equal to
+ *  the current size (i.e. one more than the current highest index) and 0
+ *  otherwise.
  *
  * Returns:
  * 	Standard Tcl completion code.  Leaves an error message in case of error.
  */
 
 int Ttk_GetContentIndexFromObj(
-    Tcl_Interp *interp, Ttk_Manager *mgr, Tcl_Obj *objPtr, Tcl_Size *indexPtr)
+    Tcl_Interp *interp, Ttk_Manager *mgr, Tcl_Obj *objPtr, int lastOK, Tcl_Size *indexPtr)
 {
     const char *string = Tcl_GetString(objPtr);
     Tcl_Size index = 0;
     Tk_Window tkwin;
 
     /* Try interpreting as an integer first:
      */
-    if (TkGetIntForIndex(objPtr, mgr->nContent - 1, 1, &index) == TCL_OK) {
-	if (index < 0 || index > mgr->nContent) {
+    if (TkGetIntForIndex(objPtr, mgr->nContent - 1, lastOK, &index) == TCL_OK) {
+	/*
+	 * Note despite passing lastOK above, we still need to check here
+	 * as well as TkGetIntForIndex only uses lastOK for end-relative indices,
+	 * not integers.
+	 */
+	if (index < 0 || (index - !!lastOK) >= mgr->nContent) {
 	    Tcl_SetObjResult(interp, Tcl_ObjPrintf(
 		"Managed window index %d out of bounds", (int)index));
 	    Tcl_SetErrorCode(interp, "TTK", "MANAGED", "INDEX", NULL);
 	    return TCL_ERROR;
 	}

Index: generic/ttk/ttkManager.h
==================================================================
--- generic/ttk/ttkManager.h
+++ generic/ttk/ttkManager.h
@@ -79,11 +79,11 @@
 MODULE_SCOPE Tcl_Size Ttk_ContentIndex(Ttk_Manager *, Tk_Window);
     /* Returns: index in content array of specified window, TCL_INDEX_NONE if not found */
 
 #define Ttk_GetSlaveIndexFromObj Ttk_GetContentIndexFromObj
 MODULE_SCOPE int Ttk_GetContentIndexFromObj(
-    Tcl_Interp *, Ttk_Manager *, Tcl_Obj *, Tcl_Size *indexPtr);
+    Tcl_Interp *, Ttk_Manager *, Tcl_Obj *, int lastOK, Tcl_Size *indexPtr);
 
 /* Accessor functions:
  */
 #define Ttk_NumberSlaves Ttk_NumberContent
 MODULE_SCOPE Tcl_Size Ttk_NumberContent(Ttk_Manager *);

Index: generic/ttk/ttkNotebook.c
==================================================================
--- generic/ttk/ttkNotebook.c
+++ generic/ttk/ttkNotebook.c
@@ -861,11 +861,11 @@
     }
 
     /* ... or integer index or content window name:
      */
     if (Ttk_GetContentIndexFromObj(
-	    interp, nb->notebook.mgr, objPtr, index_rtn) == TCL_OK)
+	    interp, nb->notebook.mgr, objPtr, 1, index_rtn) == TCL_OK)
     {
 	return TCL_OK;
     }
     if (*index_rtn == Ttk_NumberContent(nb->notebook.mgr)) {
 	Tcl_SetObjResult(interp, Tcl_ObjPrintf(
@@ -960,15 +960,10 @@
     if (objc < 4) {
 	Tcl_WrongNumArgs(interp, 2,objv, "index window ?-option value ...?");
 	return TCL_ERROR;
     }
 
-    if (TCL_OK != Ttk_GetContentIndexFromObj(
-		interp, nb->notebook.mgr, objv[2], &destIndex)) {
-	return TCL_ERROR;
-    }
-
     if (Tcl_GetString(objv[3])[0] == '.') {
 	/* Window name -- could be new or existing content window.
 	 */
 	Tk_Window window =
 	    Tk_NameToWindow(interp,Tcl_GetString(objv[3]),nb->core.tkwin);
@@ -977,19 +972,28 @@
 	    return TCL_ERROR;
 	}
 
 	srcIndex = Ttk_ContentIndex(nb->notebook.mgr, window);
 	if (srcIndex < 0) {	/* New content window */
+	    if (TCL_OK != Ttk_GetContentIndexFromObj(
+		interp, nb->notebook.mgr, objv[2], 1, &destIndex)) {
+		return TCL_ERROR;
+	    }
 	    return AddTab(interp, nb, destIndex, window, objc-4,objv+4);
 	}
     } else if (Ttk_GetContentIndexFromObj(
-		interp, nb->notebook.mgr, objv[3], &srcIndex) != TCL_OK)
+		interp, nb->notebook.mgr, objv[3], 0, &srcIndex) != TCL_OK)
     {
 	return TCL_ERROR;
     } else if (srcIndex  >= Ttk_NumberContent(nb->notebook.mgr)) {
 	srcIndex = Ttk_NumberContent(nb->notebook.mgr) - 1;
     }
+
+    if (TCL_OK != Ttk_GetContentIndexFromObj(
+	interp, nb->notebook.mgr, objv[2], 0, &destIndex)) {
+	return TCL_ERROR;
+    }
 
     /* Move existing content window:
      */
     if (ConfigureTab(interp, nb,
 	     (Tab *)Ttk_ContentData(nb->notebook.mgr, srcIndex),

Index: generic/ttk/ttkPanedwindow.c
==================================================================
--- generic/ttk/ttkPanedwindow.c
+++ generic/ttk/ttkPanedwindow.c
@@ -665,11 +665,11 @@
     if (!window) {
 	return TCL_ERROR;
     }
 
     if (TCL_OK != Ttk_GetContentIndexFromObj(
-		interp,pw->paned.mgr, objv[2], &destIndex))
+		interp,pw->paned.mgr, objv[2], 1, &destIndex))
     {
 	return TCL_ERROR;
     }
 
     srcIndex = Ttk_ContentIndex(pw->paned.mgr, window);
@@ -700,11 +700,11 @@
 	Tcl_WrongNumArgs(interp, 2,objv, "pane");
 	return TCL_ERROR;
     }
 
     if (TCL_OK != Ttk_GetContentIndexFromObj(
-		    interp, pw->paned.mgr, objv[2], &paneIndex))
+		    interp, pw->paned.mgr, objv[2], 0, &paneIndex))
     {
 	return TCL_ERROR;
     } else if (paneIndex >= Ttk_NumberContent(pw->paned.mgr)) {
 	paneIndex = Ttk_NumberContent(pw->paned.mgr) - 1;
     }
@@ -781,11 +781,11 @@
 	Tcl_WrongNumArgs(interp, 2,objv, "pane ?-option value ...?");
 	return TCL_ERROR;
     }
 
     if (TCL_OK != Ttk_GetContentIndexFromObj(
-		    interp,pw->paned.mgr, objv[2], &paneIndex))
+		    interp,pw->paned.mgr, objv[2], 0, &paneIndex))
     {
 	return TCL_ERROR;
     } else if (paneIndex >= Ttk_NumberContent(pw->paned.mgr)) {
 	paneIndex = Ttk_NumberContent(pw->paned.mgr) - 1;
     }

Index: tests/ttk/notebook.test
==================================================================
--- tests/ttk/notebook.test
+++ tests/ttk/notebook.test
@@ -551,6 +551,29 @@
     list [.w cget -style] [.w style] [winfo class .w]
 } -cleanup {
     destroy .w
 } -result {customStyle.TNotebook customStyle.TNotebook TNotebook}
 
+test notebook-9.1 "move last tab by numerical index" -body {
+    ::ttk::notebook .n
+    foreach tabs {TabA TabB TabC} {
+	::ttk::entry .n.[string tolower $tabs]
+	.n add .n.[string tolower $tabs] -text $tabs
+    }
+   .n insert 0 2  ; # allowed: TabC moves to first tab position
+   .n insert 0 3  ; # not allowed: position 3 is after last tab
+} -cleanup {
+    destroy .n
+} -result {Managed window index 3 out of bounds} -returnCodes error
+test notebook-9.2 "move first tab to last position by numerical index" -body {
+    ::ttk::notebook .n
+    foreach tabs {TabA TabB TabC} {
+	::ttk::entry .n.[string tolower $tabs]
+	.n add .n.[string tolower $tabs] -text $tabs
+    }
+   .n insert 2 0  ; # allowed: TabA moves to last tab position
+   .n insert 3 0  ; # not allowed: position 3 is after last tab
+} -cleanup {
+    destroy .n
+} -result {Managed window index 3 out of bounds} -returnCodes error
+
 tcltest::cleanupTests

Index: tests/ttk/panedwindow.test
==================================================================
--- tests/ttk/panedwindow.test
+++ tests/ttk/panedwindow.test
@@ -8,10 +8,26 @@
 # Basic sanity checks:
 #
 test panedwindow-1.0 "Setup" -body {
     ttk::panedwindow .pw
 } -result .pw
+
+test panedwindow-1.0.1 "Make sure pane 0 command doesn't crash on empty pane - bug e6140f3404" -body {
+    .pw pane 0
+} -result {Managed window index 0 out of bounds} -returnCodes error
+
+test panedwindow-1.0.2 "Make sure pane end command doesn't crash on empty pane - bug e6140f3404" -body {
+    .pw pane end
+} -result {Managed window index -1 out of bounds} -returnCodes error
+
+test panedwindow-1.0.3 "Make sure forget 0 command doesn't crash on empty pane - bug e6140f3404" -body {
+    .pw forget 0
+} -result {Managed window index 0 out of bounds} -returnCodes error
+
+test panedwindow-1.0.4 "Make sure forget end command doesn't crash on empty pane - bug e6140f3404" -body {
+    .pw forget end
+} -result {Managed window index -1 out of bounds} -returnCodes error
 
 test panedwindow-1.1 "Make sure empty panedwindow doesn't crash" -body {
     pack .pw -expand true -fill both
     update
 }