diff --git a/libswscale/graph.h b/libswscale/graph.h
index 5ffc069d5a..25aae12e4c 100644
--- a/libswscale/graph.h
+++ b/libswscale/graph.h
@@ -45,6 +45,12 @@ typedef struct SwsGraph SwsGraph;
 typedef void (*SwsPassFunc)(const SwsFrame *out, const SwsFrame *in,
                             int y, int h, const SwsPass *pass);
 
+/**
+ * Function to run from the main thread before processing any lines.
+ */
+typedef void (*SwsPassSetup)(const SwsFrame *out, const SwsFrame *in,
+                             const SwsPass *pass);
+
 /**
  * Represents an allocated output buffer for a filter pass.
  */
@@ -88,7 +94,7 @@ struct SwsPass {
     /**
      * Called once from the main thread before running the filter. Optional.
      */
-    void (*setup)(const SwsFrame *out, const SwsFrame *in, const SwsPass *pass);
+    SwsPassSetup setup;
 
     /**
      * Optional private state and associated free() function.