diff --git a/bmi_heat/CMakeLists.txt b/bmi_heat/CMakeLists.txt
index 8f86d3b..0e92921 100644
--- a/bmi_heat/CMakeLists.txt
+++ b/bmi_heat/CMakeLists.txt
@@ -1,12 +1,17 @@
 # bmi-heat
 
+set(extension_name bmiheatgeof)
+
 # Create shared library, except on Windows.
 if(WIN32)
   add_library(${bmi_name} bmi_heat.f90)
+  add_library(${extension_name} bmi_heat_geo.f90)
 else()
   add_library(${bmi_name} SHARED bmi_heat.f90)
+  add_library(${extension_name} SHARED bmi_heat_geo.f90)
 endif()
 target_link_libraries(${bmi_name} ${model_name} ${bmif_lib})
+target_link_libraries(${extension_name} ${bmi_name})
 
 add_executable(run_${bmi_name} bmi_main.f90)
 target_link_libraries(run_${bmi_name} ${bmi_name})
@@ -16,12 +21,14 @@ install(
   RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
 )
 install(
-  TARGETS ${bmi_name}
+  TARGETS ${bmi_name} ${extension_name}
   LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
   ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
   RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
 )
 install(
-  FILES ${CMAKE_Fortran_MODULE_DIRECTORY}/${bmi_name}.mod
+  FILES
+    ${CMAKE_Fortran_MODULE_DIRECTORY}/${bmi_name}.mod
+    ${CMAKE_Fortran_MODULE_DIRECTORY}/${extension_name}.mod
   DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
 )