diff --git a/tools/pioasm/c_sdk_output.cpp b/tools/pioasm/c_sdk_output.cpp
index 9e2dc22..9388c0d 100644
--- a/tools/pioasm/c_sdk_output.cpp
+++ b/tools/pioasm/c_sdk_output.cpp
@@ -68,6 +68,8 @@ struct c_sdk_output : public output_format {
 
         header(out, "This file is autogenerated by pioasm; do not edit!");
 
+        fprintf(out, "#pragma once\n");
+        fprintf(out, "\n");
         fprintf(out, "#if !PICO_NO_HARDWARE\n");
         fprintf(out, "#include \"hardware/pio.h\"\n");
         fprintf(out, "#endif\n");