diff --git a/CMakeLists.txt b/CMakeLists.txt
index e29c9dfd9c23..dee92334c92f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -662,7 +662,7 @@ endif(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
                 find_package(HDF5 COMPONENTS NO_MODULE REQUIRED static)
             else()
                 find_package(PkgConfig)
-                pkg_search_module(HDF5 REQUIRED hdf5-serial)
+                pkg_search_module(HDF5 hdf5-serial)
                 if(NOT HDF5_FOUND)
                     find_package(HDF5 REQUIRED)
                 else()
@@ -680,7 +680,7 @@ endif(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
                 endif()
 
                 # Med Fichier can require MPI
-                pkg_search_module(OPENMPI REQUIRED ompi-cxx)
+                pkg_search_module(OPENMPI ompi-cxx)
                 add_compile_options(${OPENMPI_CFLAGS})
                 link_directories(${OPENMPI_LIBRARY_DIRS})
                 link_libraries(${OPENMPI_LIBRARIES})