diff --git a/source/blender/blenlib/BLI_path_util.h b/source/blender/blenlib/BLI_path_util.h
index 56d82a34067..8f89fab0724 100644
--- a/source/blender/blenlib/BLI_path_util.h
+++ b/source/blender/blenlib/BLI_path_util.h
@@ -49,10 +49,12 @@ bool BLI_make_existing_file(const char *name);
  * - Won't change \a string.
  * - Won't create any directories.
  * - Doesn't use CWD, or deal with relative paths.
- * - Only fill's in \a dir and \a file when they are non NULL.
  */
-void BLI_path_split_dir_file(
-    const char *string, char *dir, size_t dirlen, char *file, size_t filelen);
+void BLI_path_split_dir_file(const char *string,
+                             char *dir,
+                             size_t dirlen,
+                             char *file,
+                             size_t filelen) ATTR_NONNULL(1, 2, 4);
 /**
  * Copies the parent directory part of string into `dir`, max length `dirlen`.
  */
diff --git a/source/blender/blenlib/intern/fileops.c b/source/blender/blenlib/intern/fileops.c
index dc033594fb3..bb760437c26 100644
--- a/source/blender/blenlib/intern/fileops.c
+++ b/source/blender/blenlib/intern/fileops.c
@@ -246,7 +246,7 @@ bool BLI_file_is_writable(const char *filepath)
   else {
     /* file doesn't exist -- check I can create it in parent directory */
     char parent[FILE_MAX];
-    BLI_path_split_dir_file(filepath, parent, sizeof(parent), NULL, 0);
+    BLI_path_split_dir_part(filepath, parent, sizeof(parent));
 #ifdef WIN32
     /* windows does not have X_OK */
     writable = BLI_access(parent, W_OK) == 0;
diff --git a/source/blender/blenlib/intern/path_util.c b/source/blender/blenlib/intern/path_util.c
index b9e8bbbe00c..25ecd6f911d 100644
--- a/source/blender/blenlib/intern/path_util.c
+++ b/source/blender/blenlib/intern/path_util.c
@@ -1479,6 +1479,13 @@ bool BLI_path_filename_ensure(char *filepath, size_t maxlen, const char *filenam
   return false;
 }
 
+static size_t path_split_dir_file_offset(const char *string)
+{
+  const char *lslash_str = BLI_path_slash_rfind(string);
+  const size_t lslash = lslash_str ? (size_t)(lslash_str - string) + 1 : 0;
+  return lslash;
+}
+
 void BLI_path_split_dir_file(
     const char *string, char *dir, const size_t dirlen, char *file, const size_t filelen)
 {
@@ -1486,32 +1493,37 @@ void BLI_path_split_dir_file(
   memset(dir, 0xff, sizeof(*dir) * dirlen);
   memset(file, 0xff, sizeof(*file) * filelen);
 #endif
-  const char *lslash_str = BLI_path_slash_rfind(string);
-  const size_t lslash = lslash_str ? (size_t)(lslash_str - string) + 1 : 0;
-
-  if (dir) {
-    if (lslash) {
-      /* +1 to include the slash and the last char. */
-      BLI_strncpy(dir, string, MIN2(dirlen, lslash + 1));
-    }
-    else {
-      dir[0] = '\0';
-    }
+  const size_t lslash = path_split_dir_file_offset(string);
+  if (lslash) { /* +1 to include the slash and the last char. */
+    BLI_strncpy(dir, string, MIN2(dirlen, lslash + 1));
   }
-
-  if (file) {
-    BLI_strncpy(file, string + lslash, filelen);
+  else {
+    dir[0] = '\0';
   }
+  BLI_strncpy(file, string + lslash, filelen);
 }
 
 void BLI_path_split_dir_part(const char *string, char *dir, const size_t dirlen)
 {
-  BLI_path_split_dir_file(string, dir, dirlen, NULL, 0);
+#ifdef DEBUG_STRSIZE
+  memset(dir, 0xff, sizeof(*dir) * dirlen);
+#endif
+  const size_t lslash = path_split_dir_file_offset(string);
+  if (lslash) { /* +1 to include the slash and the last char. */
+    BLI_strncpy(dir, string, MIN2(dirlen, lslash + 1));
+  }
+  else {
+    dir[0] = '\0';
+  }
 }
 
 void BLI_path_split_file_part(const char *string, char *file, const size_t filelen)
 {
-  BLI_path_split_dir_file(string, NULL, 0, file, filelen);
+#ifdef DEBUG_STRSIZE
+  memset(file, 0xff, sizeof(*file) * filelen);
+#endif
+  const size_t lslash = path_split_dir_file_offset(string);
+  BLI_strncpy(file, string + lslash, filelen);
 }
 
 const char *BLI_path_extension_or_end(const char *filepath)
diff --git a/source/blender/sequencer/intern/disk_cache.c b/source/blender/sequencer/intern/disk_cache.c
index 279bd28b8a8..88ad44be134 100644
--- a/source/blender/sequencer/intern/disk_cache.c
+++ b/source/blender/sequencer/intern/disk_cache.c
@@ -176,7 +176,7 @@ static void seq_disk_cache_get_files(SeqDiskCache *disk_cache, char *path)
     }
 
     char file[FILE_MAX];
-    BLI_path_split_dir_file(fl->path, NULL, 0, file, sizeof(file));
+    BLI_path_split_file_part(fl->path, file, sizeof(file));
 
     bool is_dir = BLI_is_dir(fl->path);
     if (is_dir && !FILENAME_IS_CURRPAR(file)) {