diff --git a/export.cpp b/export.cpp
index a1a53f8..7f6dca1 100644
--- a/export.cpp
+++ b/export.cpp
@@ -301,6 +301,7 @@ void SolveSpace::ExportAsPngTo(char *filename) {
 
     png_write_end(png_ptr, info_ptr);
     png_destroy_write_struct(&png_ptr, &info_ptr);
+    fclose(f);
     return;
 
 err: