diff --git a/CMakeLists.txt b/CMakeLists.txt
index ff78f21..9a74fe7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -159,7 +159,7 @@ ExternalProject_Add(SimGear
     UPDATE_COMMAND ""      # or update.
     SOURCE_DIR ${CMAKE_CURRENT_LIST_DIR}/simgear
     BINARY_DIR sgbuild 
-    CMAKE_ARGS ${SG_CMAKE_ARGS} -DCMAKE_INSTALL_PREFIX=${CMAKE_INSTALL_PREFIX}/${OSG_MSVC} -DCMAKE_PREFIX_PATH=${OSG_INSTALL_PREFIX}
+    CMAKE_ARGS ${SG_CMAKE_ARGS} -DCMAKE_INSTALL_PREFIX=${CMAKE_INSTALL_PREFIX}/${OSG_MSVC}/SimGear -DCMAKE_PREFIX_PATH=${OSG_INSTALL_PREFIX}
 )
 
 # on Windows, PLIB is in the 3rd-party dependencies zip
@@ -184,5 +184,5 @@ ExternalProject_Add(FlightGear
     UPDATE_COMMAND ""      # or update.
     SOURCE_DIR ${CMAKE_CURRENT_LIST_DIR}/flightgear
     BINARY_DIR fgbuild 
-    CMAKE_ARGS ${FG_CMAKE_ARGS} -DCMAKE_INSTALL_PREFIX=${CMAKE_INSTALL_PREFIX}/${OSG_MSVC} -DCMAKE_PREFIX_PATH=${OSG_INSTALL_PREFIX}
+    CMAKE_ARGS ${FG_CMAKE_ARGS} -DCMAKE_INSTALL_PREFIX=${CMAKE_INSTALL_PREFIX}/${OSG_MSVC}/FlightGear -DCMAKE_PREFIX_PATH=${OSG_INSTALL_PREFIX}
 )