diff --git a/cmake/HPX_SetupGasnet.cmake b/cmake/HPX_SetupGasnet.cmake
index 2914e0130b60..26653ac1d944 100644
--- a/cmake/HPX_SetupGasnet.cmake
+++ b/cmake/HPX_SetupGasnet.cmake
@@ -153,15 +153,23 @@ macro(hpx_setup_gasnet)
         endif()
 
         if(${MPI_C_COMPILER})
-          set(CMAKE_C_COMPILER ${MPI_C_COMPILER})
+          set(MPI_C_COMPILER ${CMAKE_C_COMPILER})
+          set(MPI_CC ${CMAKE_C_COMPILER})
+          set(ENV{MPI_CC} ${CMAKE_C_COMPILER})
         elseif(${MPI_CC})
-          set(CMAKE_C_COMPILER ${MPI_CC})
-        elseif(ENV{MPI_CC})
-          set(CMAKE_C_COMPILER ENV{MPI_CC})
+          set(MPI_CC ${CMAKE_C_COMPILER})
+          set(ENV{MPI_CC} ${CMAKE_C_COMPILER})
+        elseif($ENV{MPI_CC})
+          set(MPI_CC ${CMAKE_C_COMPILER})
+          set(ENV{MPI_CC} ${CMAKE_C_COMPILER})
         else()
           message(FATAL_ERROR "GASNet MPI Conduit selected; $MPI_CC not found!")
         endif()
 
+        if(NOT "$CMAKE_C_COMPILER" STREQUAL "${MPI_CC}")
+          message(FATAL_ERROR "GASNet MPI: $MPI_CC != $CMAKE_C_COMPILER!")
+        endif()
+
         execute_process(
           COMMAND
             bash -c