diff --git a/libavcodec/cbs.c b/libavcodec/cbs.c
index f6e371ddef..d7aa67c3af 100644
--- a/libavcodec/cbs.c
+++ b/libavcodec/cbs.c
@@ -315,6 +315,28 @@ int ff_cbs_read(CodedBitstreamContext *ctx,
                          data, size, 0);
 }
 
+/**
+ * Allocate a new internal data buffer of the given size in the unit.
+ *
+ * The data buffer will have input padding.
+ */
+static int cbs_alloc_unit_data(CodedBitstreamUnit *unit,
+                               size_t size)
+{
+    av_assert0(!unit->data && !unit->data_ref);
+
+    unit->data_ref = av_buffer_alloc(size + AV_INPUT_BUFFER_PADDING_SIZE);
+    if (!unit->data_ref)
+        return AVERROR(ENOMEM);
+
+    unit->data      = unit->data_ref->data;
+    unit->data_size = size;
+
+    memset(unit->data + size, 0, AV_INPUT_BUFFER_PADDING_SIZE);
+
+    return 0;
+}
+
 static int cbs_write_unit_data(CodedBitstreamContext *ctx,
                                CodedBitstreamUnit *unit)
 {
@@ -360,7 +382,7 @@ static int cbs_write_unit_data(CodedBitstreamContext *ctx,
 
     flush_put_bits(&pbc);
 
-    ret = ff_cbs_alloc_unit_data(unit, put_bytes_output(&pbc));
+    ret = cbs_alloc_unit_data(unit, put_bytes_output(&pbc));
     if (ret < 0)
         return ret;
 
@@ -693,23 +715,6 @@ int ff_cbs_alloc_unit_content(CodedBitstreamUnit *unit,
     return 0;
 }
 
-int ff_cbs_alloc_unit_data(CodedBitstreamUnit *unit,
-                           size_t size)
-{
-    av_assert0(!unit->data && !unit->data_ref);
-
-    unit->data_ref = av_buffer_alloc(size + AV_INPUT_BUFFER_PADDING_SIZE);
-    if (!unit->data_ref)
-        return AVERROR(ENOMEM);
-
-    unit->data      = unit->data_ref->data;
-    unit->data_size = size;
-
-    memset(unit->data + size, 0, AV_INPUT_BUFFER_PADDING_SIZE);
-
-    return 0;
-}
-
 static int cbs_insert_unit(CodedBitstreamFragment *frag,
                            int position)
 {
diff --git a/libavcodec/cbs.h b/libavcodec/cbs.h
index bd97d163b1..87ea14cd07 100644
--- a/libavcodec/cbs.h
+++ b/libavcodec/cbs.h
@@ -380,15 +380,6 @@ int ff_cbs_alloc_unit_content(CodedBitstreamUnit *unit,
 int ff_cbs_alloc_unit_content2(CodedBitstreamContext *ctx,
                                CodedBitstreamUnit *unit);
 
-
-/**
- * Allocate a new internal data buffer of the given size in the unit.
- *
- * The data buffer will have input padding.
- */
-int ff_cbs_alloc_unit_data(CodedBitstreamUnit *unit,
-                           size_t size);
-
 /**
  * Insert a new unit into a fragment with the given content.
  *