diff --git a/stb_image_write.h b/stb_image_write.h
index 98df416..782b69d 100644
--- a/stb_image_write.h
+++ b/stb_image_write.h
@@ -807,7 +807,7 @@ unsigned char * stbi_zlib_compress(unsigned char *data, int data_len, int *out_l
 
    {
       // compute adler32 on input
-      unsigned int k=0, s1=1, s2=0;
+      unsigned int s1=1, s2=0;
       int blocklen = (int) (data_len % 5552);
       j=0;
       while (j < data_len) {