diff --git a/gambit-c.spec b/gambit-c.spec
index 847e645..6a50bf9 100644
--- a/gambit-c.spec
+++ b/gambit-c.spec
@@ -1,4 +1,4 @@
-%global dirname gambc-v4_6_6-devel
+%global _dirname gambc-v4_6_6-devel
 
 # Using -O2 on ppc64 triggers ICE with gcc
 # http://www.iro.umontreal.ca/~gambit/bugzilla/show_bug.cgi?id=155
@@ -20,7 +20,7 @@ Summary:        Scheme programming system
 Group:          Development/Languages
 License:        ASL 2.0 or LGPLv2
 URL:            http://www.iro.umontreal.ca/~gambit
-Source0:        http://www.iro.umontreal.ca/~gambit/download/gambit/v4.6/source/%{dirname}.tgz
+Source0:        http://www.iro.umontreal.ca/~gambit/download/gambit/v4.6/source/%{_dirname}.tgz
 Source1:        gambit-init.el
 Patch0:         gambc-v4_2_8-modtime.patch
 Patch1:         gambc-v4_6_6-reduce-opt.patch
@@ -82,7 +82,7 @@ Elisp source file for the Gambit-C editing mode for Emacs.
 
 
 %prep
-%setup -q -n %{dirname}
+%setup -q -n %{_dirname}
 %patch0 -p1 -b .modtime
 
 %ifarch ppc64
@@ -184,6 +184,9 @@ fi
 
 
 %changelog
+* Tue Nov 05 2013 Kyle McMartin <kyle@fedoraproject.org>
+- Fix FTBFS because of dirname macro, use _dirname instead.
+
 * Sat Aug 03 2013 Fedora Release Engineering <rel-eng@lists.fedoraproject.org> - 4.6.6-4
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_20_Mass_Rebuild