--- spack-src/src/io_tools.F90	2021-10-08 13:30:58.000000000 +0900
+++ spack-src/src/io_tools.F90.new	2021-10-08 13:30:30.000000000 +0900
@@ -12,6 +12,9 @@
 #if defined (__INTEL_COMPILER)
  USE IFPORT
 #endif
+#if defined(__FUJITSU)
+use service_routines
+#endif
  IMPLICIT NONE
 
  PRIVATE
--- spack-src/src/excor.F90	2021-10-08 16:04:49.000000000 +0900
+++ spack-src/src/excor.F90.new	2021-10-08 16:12:28.000000000 +0900
@@ -11,6 +11,9 @@
 
 MODULE excor
 
+#if defined(__FUJITSU)
+  USE, intrinsic :: ieee_arithmetic
+#endif
   USE io_tools
   USE Tools
   USE globalmath
@@ -589,8 +592,15 @@
         deallocate(grad,gradmag,gxc,dgxcdr,dfxcdgbg)
         !  not sure why/if this is needed
         do i=1,n
+#if defined(__FUJITSU)
+           if (ieee_support_nan(tmpv(i))) then
+               if (ieee_is_nan(tmpv(i))) tmpv(i)=0.d0
+               if (ieee_is_nan(exci(i))) exci(i)=0.d0
+           endif
+#else
            if (isnan(tmpv(i))) tmpv(i)=0.d0
            if (isnan(exci(i))) exci(i)=0.d0
+#endif
         enddo   
        elseif (libxc_ismgga()) then
         write(std_out,*) '  atompaw not yet available for mgga -- stop '