diff --git a/src/interface.f90 b/src/interface.f90
index d614bbd..a2f1ddd 100644
--- a/src/interface.f90
+++ b/src/interface.f90
@@ -224,7 +224,7 @@ subroutine nc_initialize(self,filename,ierr, status,action,comp_lvl,verbose,debu
 integer :: ier
 
 if (self%is_open) then
-  write(stderr,*) 'WARNING:nc4fortran: file handle already open to: '// filename
+  write(stderr,*) 'WARNING:nc4fortran:initialize file handle already open to: '// filename
   return
 endif
 
@@ -287,6 +287,11 @@ subroutine nc_finalize(self, ierr)
 
 integer :: ier
 
+if(.not. self%is_open) then
+  write(stderr,*) 'WARNING:nc4fortran:finalize file handle is not open'
+  return
+endif
+
 ier = nf90_close(self%ncid)
 if (present(ierr)) ierr = ier
 if (ier /= NF90_NOERR) then
diff --git a/src/read.f90 b/src/read.f90
index bb88106..ce93a89 100644
--- a/src/read.f90
+++ b/src/read.f90
@@ -11,6 +11,9 @@
 integer :: i, tempdims(NC_MAXDIM), N, ier
 character(NF90_MAX_NAME) :: tempnames(NC_MAXDIM)
 
+
+if(.not.self%is_open) error stop 'ERROR:nc4fortran:read: file handle not open'
+
 N = 0
 do i = 1,NC_MAXDIM
   ier = nf90_inquire_dimension(self%ncid, dimid=i, name=tempnames(i), len=tempdims(i))
@@ -28,9 +31,17 @@
 
 module procedure nc_check_exist
 integer :: varid, ierr
-ierr = nf90_inq_varid(self%ncid, dname, varid)
 
 exists = .false.
+
+if(.not.self%is_open) then
+  write(stderr,*) 'WARNING:nc4fortran:read: file handle not open ' // self%filename
+  return
+endif
+
+ierr = nf90_inq_varid(self%ncid, dname, varid)
+
+
 select case (ierr)
 case (NF90_NOERR)
   exists = .true.
diff --git a/src/reader.f90 b/src/reader.f90
index 5c06cfe..9e34b34 100644
--- a/src/reader.f90
+++ b/src/reader.f90
@@ -7,6 +7,9 @@
 
 module procedure nc_read_scalar
 integer :: varid, ier
+
+if(.not.self%is_open) error stop 'ERROR:nc4fortran:reader file handle not open'
+
 ier = nf90_inq_varid(self%ncid, dname, varid)
 
 if(ier == NF90_NOERR) then
@@ -36,6 +39,9 @@
 
 module procedure nc_read_1d
 integer :: varid, ier
+
+if(.not.self%is_open) error stop 'ERROR:nc4fortran:reader file handle not open'
+
 ier = nf90_inq_varid(self%ncid, dname, varid)
 
 if(ier == NF90_NOERR) then
@@ -65,6 +71,9 @@
 
 module procedure nc_read_2d
 integer :: varid, ier
+
+if(.not.self%is_open) error stop 'ERROR:nc4fortran:reader file handle not open'
+
 ier = nf90_inq_varid(self%ncid, dname, varid)
 
 if(ier == NF90_NOERR) then
@@ -93,6 +102,9 @@
 
 module procedure nc_read_3d
 integer :: varid, ier
+
+if(.not.self%is_open) error stop 'ERROR:nc4fortran:reader file handle not open'
+
 ier = nf90_inq_varid(self%ncid, dname, varid)
 
 if(ier == NF90_NOERR) then
@@ -121,6 +133,9 @@
 
 module procedure nc_read_4d
 integer :: varid, ier
+
+if(.not.self%is_open) error stop 'ERROR:nc4fortran:reader file handle not open'
+
 ier = nf90_inq_varid(self%ncid, dname, varid)
 
 if(ier == NF90_NOERR) then
@@ -149,6 +164,9 @@
 
 module procedure nc_read_5d
 integer :: varid, ier
+
+if(.not.self%is_open) error stop 'ERROR:nc4fortran:reader file handle not open'
+
 ier = nf90_inq_varid(self%ncid, dname, varid)
 
 if(ier == NF90_NOERR) then
@@ -177,6 +195,9 @@
 
 module procedure nc_read_6d
 integer :: varid, ier
+
+if(.not.self%is_open) error stop 'ERROR:nc4fortran:reader file handle not open'
+
 ier = nf90_inq_varid(self%ncid, dname, varid)
 
 if(ier == NF90_NOERR) then
@@ -205,6 +226,9 @@
 
 module procedure nc_read_7d
 integer :: varid, ier
+
+if(.not.self%is_open) error stop 'ERROR:nc4fortran:reader file handle not open'
+
 ier = nf90_inq_varid(self%ncid, dname, varid)
 
 if(ier == NF90_NOERR) then
diff --git a/src/write.f90 b/src/write.f90
index 8d883ec..28a0cf9 100644
--- a/src/write.f90
+++ b/src/write.f90
@@ -10,6 +10,8 @@
 integer :: i, L
 character(NF90_MAX_NAME) :: name
 
+if(.not.self%is_open) error stop 'ERROR:nc4fortran:write: file handle not open'
+
 do i=1,size(dims)
   if (present(dimnames)) then
     ierr = nf90_inq_dimid(self%ncid, dimnames(i), dimids(i))
@@ -34,6 +36,8 @@
 module procedure write_attribute
 integer :: varid, ier
 
+if(.not.self%is_open) error stop 'ERROR:nc4fortran:write: file handle not open'
+
 ier = nf90_inq_varid(self%ncid, dname, varid)
 
 if(ierr == nf90_noerr) ier = nf90_put_att(self%ncid, varid, attrname, value)
diff --git a/src/writer.f90 b/src/writer.f90
index 5b7f020..e20579c 100644
--- a/src/writer.f90
+++ b/src/writer.f90
@@ -8,6 +8,8 @@
 module procedure nc_write_scalar
 integer :: varid, ier
 
+if(.not.self%is_open) error stop 'ERROR:nc4fortran:writer: file handle not open'
+
 select type (value)
 type is (real(real64))
   ier = nf90_def_var(self%ncid, dname, NF90_DOUBLE, varid=varid)