diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5ebfc73e6..882888c7a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -105,8 +105,10 @@ ADD_DEFINITIONS(-D_UNICODE=1
 INCLUDE(Version)
 
 # Let fish pick up when we're running out of the build directory without installing
-ADD_DEFINITIONS(-DCMAKE_BINARY_DIR="${CMAKE_BINARY_DIR}")
-ADD_DEFINITIONS(-DCMAKE_SOURCE_DIR="${CMAKE_SOURCE_DIR}")
+GET_FILENAME_COMPONENT(REAL_CMAKE_BINARY_DIR "${CMAKE_BINARY_DIR}" REALPATH)
+GET_FILENAME_COMPONENT(REAL_CMAKE_SOURCE_DIR "${CMAKE_SOURCE_DIR}" REALPATH)
+ADD_DEFINITIONS(-DCMAKE_BINARY_DIR="${REAL_CMAKE_BINARY_DIR}")
+ADD_DEFINITIONS(-DCMAKE_SOURCE_DIR="${REAL_CMAKE_SOURCE_DIR}")
 
 # Teach fish_version.o to rebuild when FBVF changes.
 # The standard C++ include detection machinery misses this.