2 files changed, 7 insertions, 2 deletions
diff --git a/src/nvim/os/fileio.c b/src/nvim/os/fileio.c
index 585c4964e2..89834bed80 100644
--- a/src/nvim/os/fileio.c
+++ b/src/nvim/os/fileio.c
@@ -320,9 +320,8 @@ ptrdiff_t file_write(FileDescriptor *const fp, const char *const buf, const size
   FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_NONNULL_ARG(1)
 {
   assert(fp->wr);
-  ptrdiff_t space = (fp->buffer + ARENA_BLOCK_SIZE) - fp->write_pos;
   // includes the trivial case of size==0
-  if (size < (size_t)space) {
+  if (size < file_space(fp)) {
     memcpy(fp->write_pos, buf, size);
     fp->write_pos += size;
     return (ptrdiff_t)size;
diff --git a/src/nvim/os/fileio.h b/src/nvim/os/fileio.h
index e8fd2209db..523f9657a4 100644
--- a/src/nvim/os/fileio.h
+++ b/src/nvim/os/fileio.h
@@ -2,6 +2,7 @@
 
 #include <stddef.h>  // IWYU pragma: keep
 
+#include "nvim/memory_defs.h"
 #include "nvim/os/fileio_defs.h"  // IWYU pragma: keep
 
 /// file_open() flags
@@ -32,6 +33,11 @@ enum {
   kRWBufferSize = 1024,
 };
 
+static inline size_t file_space(FileDescriptor *fp)
+{
+  return (size_t)((fp->buffer + ARENA_BLOCK_SIZE) - fp->write_pos);
+}
+
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "os/fileio.h.generated.h"
 #endif