diff --git a/Fortran/FUNC_sign.f90 b/Fortran/FUNC_sign.f90
index 19d7669..c499f31 100644
--- a/Fortran/FUNC_sign.f90
+++ b/Fortran/FUNC_sign.f90
@@ -5,7 +5,7 @@
     
     real*8 :: A
     if(isnan(A)) then
-        FUNC_sign = sqrt(-1.0)
+        FUNC_sign = A
     elseif(A>0) then
         FUNC_sign = 1.0
     elseif(A<0) then