diff --git a/gen/libpng/generator.toml b/gen/libpng/generator.toml
index 87f1c01..862e8e5 100644
--- a/gen/libpng/generator.toml
+++ b/gen/libpng/generator.toml
@@ -1,6 +1,6 @@
 [general]
 library_name = "libpng"
-output_file_path = "libpng.jl"
+output_file_path = "libpng_api.jl"
 prologue_file_path = "prologue.jl"
 use_julia_native_enum_type = false
 print_using_CEnum = false
diff --git a/gen/libpng/libpng.jl b/gen/libpng/libpng_api.jl
similarity index 99%
rename from gen/libpng/libpng.jl
rename to gen/libpng/libpng_api.jl
index 6eb643e..da00fca 100644
--- a/gen/libpng/libpng.jl
+++ b/gen/libpng/libpng_api.jl
@@ -654,7 +654,7 @@ function png_get_error_ptr(png_ptr)
 end
 
 function png_set_write_fn(png_ptr, io_ptr, write_data_fn, output_flush_fn)
-    ccall((:png_set_write_fn, libpng), Cvoid, (png_structrp, png_voidp, png_rw_ptr, png_flush_ptr), png_ptr, io_ptr, write_data_fn, output_flush_fn)
+    ccall((:png_set_write_fn, libpng), Cvoid, (png_structrp, Any, png_rw_ptr, png_flush_ptr), png_ptr, io_ptr, write_data_fn, output_flush_fn)
 end
 
 function png_set_read_fn(png_ptr, io_ptr, read_data_fn)
diff --git a/gen/libpng/wrap_libpng.jl b/gen/libpng/wrap_libpng.jl
index 52aa162..8b3ee55 100644
--- a/gen/libpng/wrap_libpng.jl
+++ b/gen/libpng/wrap_libpng.jl
@@ -1,6 +1,19 @@
 using Clang.Generators
 using libpng_jll
 
+function rewrite(ex::Expr)
+    if Meta.isexpr(ex, :function) && ex.args[1].args[1] == :png_set_write_fn
+        ex = quote
+            function png_set_write_fn(png_ptr, io_ptr, write_data_fn, output_flush_fn)
+                ccall((:png_set_write_fn, libpng), Cvoid, (png_structrp, Any, png_rw_ptr, png_flush_ptr), png_ptr, io_ptr, write_data_fn, output_flush_fn)
+            end
+        end |> Base.remove_linenums!
+        ex.args[]
+    else
+        ex
+    end
+end
+
 cd(@__DIR__)
 
 include_dir = joinpath(libpng_jll.artifact_dir, "include") |> normpath
@@ -22,4 +35,10 @@ headers = [joinpath(header_dir, "png.h")]
 ctx = create_context(headers, args, options)
 
 # run generator
-build!(ctx)
\ No newline at end of file
+build!(ctx, BUILDSTAGE_NO_PRINTING)
+for node in get_nodes(ctx.dag)
+    for (i, expr) in enumerate(node.exprs)
+        node.exprs[i] = rewrite(expr)
+    end
+end
+build!(ctx, BUILDSTAGE_PRINTING_ONLY)
diff --git a/src/PNGFiles.jl b/src/PNGFiles.jl
index fa2f964..14fc249 100644
--- a/src/PNGFiles.jl
+++ b/src/PNGFiles.jl
@@ -9,7 +9,7 @@ using libpng_jll
 
 libpng_wrap_dir = joinpath(@__DIR__, "..", "gen", "libpng")
 using CEnum
-include(joinpath(libpng_wrap_dir, "libpng.jl"))
+include(joinpath(libpng_wrap_dir, "libpng_api.jl"))
 
 const readcallback_c = Ref{Ptr{Cvoid}}(C_NULL)
 const readcallback_iobuffer_c = Ref{Ptr{Cvoid}}(C_NULL)