diff --git a/CMakeLists.txt b/CMakeLists.txt
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,13 +1,24 @@
 CMAKE_MINIMUM_REQUIRED(VERSION 2.6)
 
-IF(EXISTS ${CMAKE_SOURCE_DIR}/cmake/version.cmake)
-  INCLUDE(${CMAKE_SOURCE_DIR}/cmake/version.cmake)
-ELSE(EXISTS ${CMAKE_SOURCE_DIR}/cmake/version.cmake)
-  SET(PROJECT_NAME "LEMON")
-  SET(PROJECT_VERSION "hg-tip" CACHE STRING "LEMON version string.")
-ENDIF(EXISTS ${CMAKE_SOURCE_DIR}/cmake/version.cmake)
+SET(PROJECT_NAME "LEMON")
+PROJECT(${PROJECT_NAME})
 
-PROJECT(${PROJECT_NAME})
+IF(EXISTS ${PROJECT_SOURCE_DIR}/cmake/version.cmake)
+  INCLUDE(${PROJECT_SOURCE_DIR}/cmake/version.cmake)
+ELSEIF(DEFINED ENV{LEMON_VERSION})
+  SET(LEMON_VERSION $ENV{LEMON_VERSION} CACHE STRING "LEMON version string.")
+ELSE()
+  EXECUTE_PROCESS(
+    COMMAND hg id -i
+    WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
+    OUTPUT_VARIABLE HG_REVISION
+    ERROR_QUIET
+    OUTPUT_STRIP_TRAILING_WHITESPACE
+  )
+  SET(LEMON_VERSION ${HG_REVISION} CACHE STRING "LEMON version string.")
+ENDIF()
+
+SET(PROJECT_VERSION ${LEMON_VERSION})
 
 SET(CMAKE_MODULE_PATH ${PROJECT_SOURCE_DIR}/cmake)