diff --git a/build_tools/before_all_mac.sh b/build_tools/before_all_mac.sh
index 158d3f6..fa4783e 100755
--- a/build_tools/before_all_mac.sh
+++ b/build_tools/before_all_mac.sh
@@ -9,4 +9,7 @@ export LDFLAGS="-L$(brew --prefix libomp)/lib"
 export CPPFLAGS="-I$(brew --prefix libomp)/include -I$(brew --prefix eigen@3)/include"
 export CXXFLAGS="-I$(brew --prefix libomp)/include"
 
+export CMAKE_PREFIX_PATH="$(brew --prefix eigen@3):${CMAKE_PREFIX_PATH:-}"
+export PKG_CONFIG_PATH="$(brew --prefix eigen@3)/share/pkgconfig:${PKG_CONFIG_PATH:-}"
+
 bash build_tools/build_iqtree.sh