diff --git a/cmake/Modules/SetFortranFlags.cmake b/cmake/Modules/SetFortranFlags.cmake
index ce7f3149b..0d06920de 100644
--- a/cmake/Modules/SetFortranFlags.cmake
+++ b/cmake/Modules/SetFortranFlags.cmake
@@ -75,6 +75,12 @@ SET_COMPILE_FLAG(CMAKE_Fortran_FLAGS "${CMAKE_Fortran_FLAGS}"
 SET_COMPILE_FLAG(CMAKE_Fortran_FLAGS "${CMAKE_Fortran_FLAGS}"
                 Fortran "-fno-underscoring" # GNU
                 ) 
+# Compile code assuming that IEEE signaling NaNs may generate user-visible traps during floating-point operations. 
+# Setting this option disables optimizations that may change the number of exceptions visible with signaling NaNs. 
+SET_COMPILE_FLAG(CMAKE_Fortran_FLAGS "${CMAKE_Fortran_FLAGS}"
+                Fortran "-fsignaling-nans " # GNU
+                ) 
+               
 
 # Determines whether the current Fortran Standard behavior of the compiler is fully implemented. 
 SET_COMPILE_FLAG(CMAKE_Fortran_Flags "${CMAKE_Fortran_FLAGS}"
@@ -208,6 +214,7 @@ SET_COMPILE_FLAG(CMAKE_Fortran_FLAGS_DEBUG "${CMAKE_Fortran_FLAGS_DEBUG}"
 SET_COMPILE_FLAG(CMAKE_Fortran_FLAGS_DEBUG "${CMAKE_Fortran_FLAGS_DEBUG}"
                 Fortran "-init=snan,arrays"  # Intel
                         "/Qinit:snan,arrays" # Intel Windows
+                        "-finit-real=snan"   # GNU
                 )
 
 # Does not generate an interface block for each routine in a source file
@@ -342,6 +349,11 @@ SET_COMPILE_FLAG(CMAKE_Fortran_FLAGS_RELEASE "${CMAKE_Fortran_FLAGS_RELEASE}"
 SET_COMPILE_FLAG(STRICTMATH_FLAGS "${STRICTMATH_FLAGS}"
                 Fortran "-fp-model=precise" # Intel
                          "/fp:precise" # Intel Windows 
+                         "-fno-unsafe-math-optimizations" # GNU
+                )
+# Disable transformations and optimizations that assume default floating-point rounding behavior. 
+SET_COMPILE_FLAG(STRICTMATH_FLAGS "${STRICTMATH_FLAGS}"
+                Fortran "-frounding-math"
                 )
 
 SET_COMPILE_FLAG(STRICTMATH_FLAGS "${STRICTMATH_FLAGS}"
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index ef23fadc8..e241d3360 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -14,6 +14,8 @@
 # Add the source files
 SET(STRICT_MATH_FILES
             ${SRC}/collision/collision_generate.f90
+            ${SRC}/collision/collision_io.f90     
+            ${SRC}/collision/collision_util.f90
             ${SRC}/fraggle/fraggle_generate.f90
             ${SRC}/fraggle/fraggle_util.f90
             ${SRC}/fraggle/fraggle_module.f90
@@ -31,6 +33,7 @@ SET(STRICT_MATH_FILES
             ${SRC}/rmvs/rmvs_step.f90
             ${SRC}/swiftest/swiftest_drift.f90    
             ${SRC}/swiftest/swiftest_gr.f90       
+            ${SRC}/swiftest/swiftest_io.f90         
             ${SRC}/swiftest/swiftest_kick.f90 
             ${SRC}/swiftest/swiftest_user.f90
             ${SRC}/swiftest/swiftest_obl.f90    
@@ -60,10 +63,8 @@ SET(FAST_MATH_FILES
             ${SRC}/helio/helio_module.f90
             ${SRC}/symba/symba_module.f90
             ${SRC}/collision/collision_check.f90  
-            ${SRC}/collision/collision_io.f90     
             ${SRC}/collision/collision_regime.f90   
             ${SRC}/collision/collision_resolve.f90  
-            ${SRC}/collision/collision_util.f90
             ${SRC}/encounter/encounter_check.f90
             ${SRC}/encounter/encounter_io.f90
             ${SRC}/encounter/encounter_util.f90
@@ -73,7 +74,6 @@ SET(FAST_MATH_FILES
             ${SRC}/rmvs/rmvs_encounter_check.f90
             ${SRC}/rmvs/rmvs_util.f90
             ${SRC}/swiftest/swiftest_discard.f90  
-            ${SRC}/swiftest/swiftest_io.f90         
             ${SRC}/swiftest/swiftest_util.f90
             ${SRC}/symba/symba_discard.f90
             ${SRC}/symba/symba_encounter_check.f90
diff --git a/src/swiftest/swiftest_io.f90 b/src/swiftest/swiftest_io.f90
index c3061858b..921ea8308 100644
--- a/src/swiftest/swiftest_io.f90
+++ b/src/swiftest/swiftest_io.f90
@@ -1067,7 +1067,7 @@ module subroutine swiftest_io_netcdf_get_valid_masks(self, plmask, tpmask)
          if (status == NF90_NOERR) then
             allocate(body_status(idmax))
             call netcdf_io_check( nf90_get_var(self%id, self%status_varid, body_status, start=[1, tslot], count=[idmax,1]), "swiftest_io_netcdf_get_valid_masks nf90_getvar status_varid"  )
-            lvalid(:) = body_status /= INACTIVE
+            lvalid(:) = body_status(:) /= INACTIVE
          else
             status = nf90_inq_varid(self%id, self%rh_varname, self%rh_varid) 
             if (status == NF90_NOERR) then