diff --git a/Modules.changes b/Modules.changes
index 3c5192e..384eb00 100644
--- a/Modules.changes
+++ b/Modules.changes
@@ -1,3 +1,9 @@
+-------------------------------------------------------------------
+Thu Aug  1 14:50:06 UTC 2013 - max@suse.com
+
+- Set -DUSE_INTERP_RESULT and -DUSE_INTERP_ERRORLINE" to fix build
+  with Tcl 8.6.
+
 -------------------------------------------------------------------
 Mon Feb  4 09:06:23 UTC 2013 - coolo@suse.com
 
diff --git a/Modules.spec b/Modules.spec
index d2c64bd..186ed2d 100644
--- a/Modules.spec
+++ b/Modules.spec
@@ -65,7 +65,8 @@ Authors:
 %build
 aclocal --force -I config
 autoreconf --force --install
-CFLAGS="$RPM_OPT_FLAGS -fno-strict-aliasing" ./configure \
+CFLAGS="$RPM_OPT_FLAGS -fno-strict-aliasing -DUSE_INTERP_RESULT -DUSE_INTERP_ERRORLINE" \
+./configure \
                 --prefix=/usr \
                 --with-version-path=/usr/share/modules \
                 --with-module-path=/usr/share/modules/modulefiles \