diff --git a/mail/thunderbird/Makefile b/mail/thunderbird/Makefile
--- a/mail/thunderbird/Makefile
+++ b/mail/thunderbird/Makefile
@@ -20,7 +20,6 @@
 		libvpx>=1.8.2:multimedia/libvpx \
 		${PYTHON_PKGNAMEPREFIX}sqlite3>0:databases/py-sqlite3@${PY_FLAVOR} \
 		v4l_compat>0:multimedia/v4l_compat \
-		autoconf-2.13:devel/autoconf213 \
 		nasm:devel/nasm \
 		yasm:devel/yasm \
 		zip:archivers/zip
@@ -58,9 +57,10 @@
 		${WRKSRC}/comm/mail/app/nsMailApp.cpp
 
 pre-configure:
-	(cd ${WRKSRC} && ${LOCALBASE}/bin/autoconf-2.13)
-	(cd ${MOZSRC} && ${LOCALBASE}/bin/autoconf-2.13)
-	(cd ${MOZSRC}/js/src/ && ${LOCALBASE}/bin/autoconf-2.13)
+.for _c in configure js/src/configure
+	${SED} '1,/^:/d' ${WRKSRC}/${_c}.in > ${WRKSRC}/${_c} && \
+		chmod +x ${WRKSRC}/${_c}
+.endfor
 
 port-pre-install:
 	${MKDIR} ${STAGEDIR}${PREFIX}/lib/${PORTNAME}/defaults
diff --git a/www/firefox-esr/Makefile b/www/firefox-esr/Makefile
--- a/www/firefox-esr/Makefile
+++ b/www/firefox-esr/Makefile
@@ -23,7 +23,6 @@
 		libvpx>=1.8.2:multimedia/libvpx \
 		${PYTHON_PKGNAMEPREFIX}sqlite3>0:databases/py-sqlite3@${PY_FLAVOR} \
 		v4l_compat>0:multimedia/v4l_compat \
-		autoconf-2.13:devel/autoconf213 \
 		nasm:devel/nasm \
 		yasm:devel/yasm \
 		zip:archivers/zip
@@ -52,8 +51,10 @@
 		${WRKSRC}/browser/app/nsBrowserApp.cpp
 
 pre-configure:
-	(cd ${WRKSRC} && ${LOCALBASE}/bin/autoconf-2.13)
-	(cd ${WRKSRC}/js/src/ && ${LOCALBASE}/bin/autoconf-2.13)
+.for _c in configure js/src/configure
+	${SED} '1,/^:/d' ${WRKSRC}/${_c}.in > ${WRKSRC}/${_c} && \
+		chmod +x ${WRKSRC}/${_c}
+.endfor
 
 post-install:
 	${INSTALL_DATA} ${FIREFOX_DESKTOP} ${STAGEDIR}${PREFIX}/share/applications/
diff --git a/www/firefox/Makefile b/www/firefox/Makefile
--- a/www/firefox/Makefile
+++ b/www/firefox/Makefile
@@ -21,7 +21,6 @@
 		libvpx>=1.8.2:multimedia/libvpx \
 		${PYTHON_PKGNAMEPREFIX}sqlite3>0:databases/py-sqlite3@${PY_FLAVOR} \
 		v4l_compat>0:multimedia/v4l_compat \
-		autoconf-2.13:devel/autoconf213 \
 		nasm:devel/nasm \
 		yasm:devel/yasm \
 		zip:archivers/zip
@@ -63,8 +62,10 @@
 		${WRKSRC}/browser/app/nsBrowserApp.cpp
 
 pre-configure:
-	(cd ${WRKSRC} && ${LOCALBASE}/bin/autoconf-2.13)
-	(cd ${WRKSRC}/js/src/ && ${LOCALBASE}/bin/autoconf-2.13)
+.for _c in configure js/src/configure
+	${SED} '1,/^:/d' ${WRKSRC}/${_c}.in > ${WRKSRC}/${_c} && \
+		chmod +x ${WRKSRC}/${_c}
+.endfor
 
 post-install:
 	${INSTALL_DATA} ${FIREFOX_DESKTOP} ${STAGEDIR}${PREFIX}/share/applications/