diff --git a/gcl-2.6.10-tcl8.patch b/gcl-2.6.10-tcl8.patch
new file mode 100644
index 0000000..a8b5abc
--- /dev/null
+++ b/gcl-2.6.10-tcl8.patch
@@ -0,0 +1,101 @@
+--- gcl-tk/tkMain.c.orig	2014-02-05 09:12:48.539168683 -0700
++++ gcl-tk/tkMain.c	2014-02-05 09:24:13.138923809 -0700
+@@ -42,6 +42,11 @@
+ #if (TK_MINOR_VERSION==0 && TK_MAJOR_VERSION==4)
+ #define TkCreateMainWindow Tk_CreateMainWindow
+ #endif
++#if TCL_MAJOR_VERSION >= 8
++#define INTERP_RESULT(interp) Tcl_GetStringResult(interp)
++#else
++#define INTERP_RESULT(interp) (interp)->result
++#endif
+ 
+ 
+ /*-------------------------------------------------------------------*/
+@@ -206,7 +211,7 @@
+ 
+     if (Tk_ParseArgv(interp, (Tk_Window) NULL, &argc, (const char **)argv, argTable, 0)
+ 	    != TCL_OK) {
+-	fprintf(stderr, "%s\n", interp->result);
++	fprintf(stderr, "%s\n", INTERP_RESULT(interp));
+ 	exit(1);
+     }
+     if (name == NULL) {
+@@ -239,7 +244,7 @@
+ 
+ /*     mainWindow = TkCreateMainWindow(interp, display, name/\*  , "Tk" *\/);  */
+ /*     if (mainWindow == NULL) { */
+-/* 	fprintf(stderr, "%s\n", interp->result); */
++/* 	fprintf(stderr, "%s\n", INTERP_RESULT(interp)); */
+ /* 	exit(1); */
+ /*     } */
+ /* #ifndef __MINGW32__     */
+@@ -290,7 +295,7 @@
+      */
+ 
+     if (Tcl_AppInit(interp) != TCL_OK) {
+-	fprintf(stderr, "Tcl_AppInit failed: %s\n", interp->result);
++	fprintf(stderr, "Tcl_AppInit failed: %s\n", INTERP_RESULT(interp));
+     }
+ 
+     /*
+@@ -300,7 +305,7 @@
+     if (geometry != NULL) {
+ 	code = Tcl_VarEval(interp, "wm geometry . ", geometry, (char *) NULL);
+ 	if (code != TCL_OK) {
+-	    fprintf(stderr, "%s\n", interp->result);
++	    fprintf(stderr, "%s\n", INTERP_RESULT(interp));
+ 	}
+     }
+ 
+@@ -330,13 +335,13 @@
+     
+ 	    fullName = Tcl_TildeSubst(interp, tcl_RcFileName, &buffer);
+ 	    if (fullName == NULL) {
+-		fprintf(stderr, "%s\n", interp->result);
++		fprintf(stderr, "%s\n", INTERP_RESULT(interp));
+ 	    } else {
+ 		f = fopen(fullName, "r");
+ 		if (f != NULL) {
+ 		    code = Tcl_EvalFile(interp, fullName);
+ 		    if (code != TCL_OK) {
+-			fprintf(stderr, "%s\n", interp->result);
++			fprintf(stderr, "%s\n", INTERP_RESULT(interp));
+ 		    }
+ 		    fclose(f);
+ 		}
+@@ -371,7 +376,7 @@
+ error:
+     msg = Tcl_GetVar(interp, "errorInfo", TCL_GLOBAL_ONLY);
+     if (msg == NULL) {
+-	msg = interp->result;
++	msg = INTERP_RESULT(interp);
+     }
+     dfprintf(stderr, "%s\n", msg);
+     Tcl_Eval(interp, errorExitCmd);
+@@ -496,13 +501,13 @@
+ 	      || code)
+ 	    {
+ 	      char buf[4];
+-	      char *p = buf;
++	      char *p = buf, *string;
+ 	      /*header */
+ 	      *p++ = (code ? '1' : '0');
+ 	      bcopy(msg->msg_id,p,3);
+ 	      /* end header */
+-	      if(sock_write_str2(dsfd, m_reply, buf, 4 ,
+-				 interp->result, strlen(interp->result))
++	      string = INTERP_RESULT(interp);
++	      if(sock_write_str2(dsfd, m_reply, buf, 4, string, strlen(string))
+ 		 < 0)
+ 		{		/* what do we want to do if the write failed */}
+ 	      
+@@ -686,7 +691,7 @@
+   code = Tcl_Eval(interp, szCmd);
+   if (code != TCL_OK)
+     {
+-      dfprintf(stderr, "TCL Error int bind : %s\n", interp->result);
++      dfprintf(stderr, "TCL Error int bind : %s\n", INTERP_RESULT(interp));
+ 
+     }
+   return code;
diff --git a/gcl.spec b/gcl.spec
index 313ebe8..3f959d5 100644
--- a/gcl.spec
+++ b/gcl.spec
@@ -7,7 +7,7 @@
 
 Name:           gcl
 Version:        2.6.10
-Release:        1%{?dist}
+Release:        2%{?dist}
 Summary:        GNU Common Lisp
 
 Group:          Development/Languages
@@ -80,6 +80,9 @@ Patch15:        %{name}-2.6.8-reloc-type.patch
 Patch16:        %{name}-2.6.10-largefile.patch
 # Applied upstream.  This patch fixes a broken sprintf call in the TCL code.
 Patch17:        %{name}-2.6.8-tcl.patch
+# Submitted upstream by Andrey Grozin.  Adapt to TCL 8.6 where interp->result
+# must be replaced by Tcl_GetStringResult(interp).
+Patch18:        %{name}-2.6.10-tcl8.patch
 
 BuildRequires:  libXaw-devel
 BuildRequires:  readline-devel
@@ -183,6 +186,7 @@ gcl_exec_t.
 %patch15
 %patch16
 %patch17
+%patch18
 
 # Ensure the frame pointer doesn't get added back
 sed -i 's/"-fomit-frame-pointer"/""/' configure
@@ -340,6 +344,9 @@ fi
 
 
 %changelog
+* Wed Feb  5 2014 Jerry James <loganjerry@gmail.com> - 2.6.10-2
+- Add -tcl8 patch to prepare for TCL 8.6
+
 * Fri Nov 15 2013 Jerry James <loganjerry@gmail.com> - 2.6.10-1
 - New upstream release
 - Drop upstreamed patches