diff --git a/dlib/cmake_utils/find_blas.cmake b/dlib/cmake_utils/find_blas.cmake
index 806b938..507f871 100644
--- a/dlib/cmake_utils/find_blas.cmake
+++ b/dlib/cmake_utils/find_blas.cmake
@@ -438,7 +438,7 @@ endif()
 # If using lapack, determine whether to mangle functions
 if (lapack_found)
    include(CheckFortranFunctionExists)
-   set(CMAKE_REQUIRED_LIBRARIES ${lapack_libraries})
+   set(CMAKE_REQUIRED_LIBRARIES ${lapack_libraries} ${blas_libraries})
 
    check_function_exists("sgesv" LAPACK_FOUND_C_UNMANGLED)
    check_function_exists("sgesv_" LAPACK_FOUND_C_MANGLED)