diff --git a/extern/CMakeLists.txt b/extern/CMakeLists.txt

index 35da67d05a4..1c8ae6bd5df 100644

--- a/extern/CMakeLists.txt

+++ b/extern/CMakeLists.txt

@@ -70,7 +70,9 @@ if(WITH_LIBMV OR WITH_GTESTS OR (WITH_CYCLES AND WITH_CYCLES_LOGGING))

   if(NOT WITH_SYSTEM_GFLAGS)

     add_subdirectory(gflags)

   endif()

-  add_subdirectory(glog)

+  if(NOT WITH_SYSTEM_GLOG)

+    add_subdirectory(glog)

+  endif()

 endif()

 if(WITH_GTESTS)

diff --git a/extern/ceres/CMakeLists.txt b/extern/ceres/CMakeLists.txt

index b723a4466fb..58f64f23fd8 100644

--- a/extern/ceres/CMakeLists.txt

+++ b/extern/ceres/CMakeLists.txt

@@ -8,6 +8,12 @@ set(INC

   config

 )

+if(NOT WITH_SYSTEM_GFLAGS)

+  list(APPEND INC

+    ../gflags/src

+  )

+endif()

+

 set(INC_SYS

   ${EIGEN3_INCLUDE_DIRS}

   ${GFLAGS_INCLUDE_DIRS}

diff --git a/extern/glog/CMakeLists.txt b/extern/glog/CMakeLists.txt

index f25c72d830e..bb0dd29d153 100644

--- a/extern/glog/CMakeLists.txt

+++ b/extern/glog/CMakeLists.txt

@@ -3,7 +3,6 @@

 set(INC

   src

-  ../gflags/src

 )

 set(INC_SYS

@@ -46,6 +45,9 @@ set(LIB

 )

 if(NOT WITH_SYSTEM_GFLAGS)

+  list(APPEND INC

+    ../gflags/src

+  )

   list(APPEND LIB

     extern_gflags

   )