diff --git a/CMakeLists.txt b/CMakeLists.txt
index 022ede79..669bd876 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -508,9 +508,7 @@ add_custom_command(OUTPUT ${STA_TCL_INIT}
 #
 ################################################################
 
-find_package(TCL)
-message(STATUS "TCL lib: ${TCL_LIB}")
-message(STATUS "TCL header: ${TCL_HEADER}")
+include(FindTcl)
 
 # Zlib
 include(FindZLIB)
diff --git a/cmake/FindTcl.cmake b/cmake/FindTcl.cmake
new file mode 100644
index 00000000..16920160
--- /dev/null
+++ b/cmake/FindTcl.cmake
@@ -0,0 +1,76 @@
+# OpenSTA, Static Timing Analyzer
+# Copyright (c) 2019, Parallax Software, Inc.
+# 
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+################################################################
+#
+# Locate TCL library.
+#
+# Note that the cmake findTcl module is hopeless for OSX
+# because there doesn't appear to be a way to override
+# searching OSX system directories before unix directories.
+
+set(TCL_POSSIBLE_NAMES tcl87 tcl8.7
+  tcl86 tcl8.6
+  tcl85 tcl8.5
+  tcl84 tcl8.4
+  tcl83 tcl8.3
+  tcl82 tcl8.2
+  )
+
+# tcl lib path guesses.
+if (NOT TCL_LIB_PATHS)
+  if (CMAKE_SYSTEM_NAME STREQUAL "Darwin")
+    set(TCL_LIB_PATHS /usr/local/lib)
+    set(TCL_NO_DEFAULT_PATH TRUE)
+  endif()
+elseif (CMAKE_SYSTEM_NAME STREQUAL "Linux")
+  set(TCL_LIB_PATHS /usr/lib
+    /usr/local/lib
+    )
+  set(TCL_NO_DEFAULT_PATH FALSE)
+endif()
+
+if (NOT TCL_LIB)
+  # bagbiter cmake doesn't have a way to pass NO_DEFAULT_PATH as a parameter.
+  if (TCL_NO_DEFAULT_PATH)
+    find_library(TCL_LIB
+      NAMES tcl ${TCL_POSSIBLE_NAMES}
+      PATHS ${TCL_LIB_PATHS}
+      NO_DEFAULT_PATH
+      )
+  else()
+    find_library(TCL_LIB
+      NAMES tcl ${TCL_POSSIBLE_NAMES}
+      PATHS ${TCL_LIB_PATHS}
+      )
+  endif()
+endif()
+message(STATUS "TCL lib: ${TCL_LIB}")
+
+get_filename_component(TCL_LIB_DIR "${TCL_LIB}" PATH)
+get_filename_component(TCL_LIB_PARENT1 "${TCL_LIB_DIR}" PATH)
+get_filename_component(TCL_LIB_PARENT2 "${TCL_LIB_PARENT1}" PATH)
+
+# Locate tcl.h
+if (NOT TCL_HEADER)
+  find_file(TCL_HEADER tcl.h
+    PATHS ${TCL_LIB_PARENT1} ${TCL_LIB_PARENT2}
+    PATH_SUFFIXES include include/tcl
+    NO_DEFAULT_PATH
+    )
+endif()
+message(STATUS "TCL header: ${TCL_HEADER}")
+get_filename_component(TCL_HEADER_DIR "${TCL_HEADER}" PATH)