diff --git a/root.spec b/root.spec
index fbdc63cffeb..284a7eb9afb 100644
--- a/root.spec
+++ b/root.spec
@@ -2,8 +2,8 @@
 ## INITENV +PATH PYTHON27PATH %{i}/lib
 ## INITENV +PATH PYTHON3PATH %{i}/lib
 ## INITENV SET ROOTSYS %{i}
-%define tag b475b65b36ae652c1af64f45e2629aec06dc83df
-%define branch cms/master/c6edc31
+%define tag a621b7a2e9352b55e350c24971f00b69642956d9
+%define branch cms/master/db49a85
 %define github_user cms-sw
 Source: git+https://github.com/%{github_user}/root.git?obj=%{branch}/%{tag}&export=%{n}-%{realversion}&output=/%{n}-%{realversion}-%{tag}.tgz
 
@@ -136,7 +136,7 @@ cmake ../%{n}-%{realversion} \
   -DLIBLZ4_LIBRARY="${LZ4_ROOT}/lib/liblz4.%{soext}" \
   -DZLIB_ROOT="${ZLIB_ROOT}" \
   -DZLIB_INCLUDE_DIR="${ZLIB_ROOT}/include" \
-  -DCMAKE_PREFIX_PATH="${XZ_ROOT};${OPENSSL_ROOT};${GIFLIB_ROOT};${FREETYPE_ROOT};${PYTHON_ROOT};${LIBPNG_ROOT};${PCRE_ROOT};${TBB_ROOT};${OPENBLAS_ROOT};${DAVIX_ROOT};${LZ4_ROOT};${LIBXML2_ROOT}"
+  -DCMAKE_PREFIX_PATH="${GSL_ROOT};${XZ_ROOT};${OPENSSL_ROOT};${GIFLIB_ROOT};${FREETYPE_ROOT};${PYTHON_ROOT};${LIBPNG_ROOT};${PCRE_ROOT};${TBB_ROOT};${OPENBLAS_ROOT};${DAVIX_ROOT};${LZ4_ROOT};${LIBXML2_ROOT}"
 
 # For CMake cache variables: http://www.cmake.org/cmake/help/v3.2/manual/cmake-language.7.html#lists
 # For environment variables it's OS specific: http://www.cmake.org/Wiki/CMake_Useful_Variables