diff --git a/resource_embedder.c b/resource_embedder.c
index 646be68..84fc037 100644
--- a/resource_embedder.c
+++ b/resource_embedder.c
@@ -117,6 +117,7 @@ void write_header(FILE* out_file, const char* out_file_path){
         "#endif\n"
         "\n"
         "#include <stdint.h>\n"
+        "#include <stddef.h>\n"
         "\n"
         "typedef struct {\n"
         "    const char* path;\n"
@@ -189,7 +190,7 @@ void process_file(const char* input_file_path,
 
     // writing input file content
     int byte=0;
-    size_t size=0;
+    long long unsigned int size=0;
     while( (byte=fgetc(input_file)) != EOF ){
         if(size%16==0)
             fprintf(out_file, "\n      ");