diff --git a/libmineziper/include/libmineziper_zip.h b/libmineziper/include/libmineziper_zip.h
index 9bfa5e1..dd680ff 100644
--- a/libmineziper/include/libmineziper_zip.h
+++ b/libmineziper/include/libmineziper_zip.h
@@ -25,8 +25,8 @@ typedef struct LFH
   int crc32;
   int compressed_size;
   int uncompressed_size;
-  short filename_length;
-  short extraf_length;
+  unsigned short filename_length;
+  unsigned short extraf_length;
 } LFH;
 
 typedef struct CDH
@@ -41,9 +41,9 @@ typedef struct CDH
   int crc32;
   int compressed_size;
   int uncompressed_size;
-  short filename_length;
-  short extraf_length;
-  short file_comment_length;
+  unsigned short filename_length;
+  unsigned short extraf_length;
+  unsigned short file_comment_length;
   short disk_number_start;
   short internal_file_attributes;
   int external_file_attributes;
diff --git a/libmineziper/src/libmineziper_zip.c b/libmineziper/src/libmineziper_zip.c
index 63c2022..7d6f892 100644
--- a/libmineziper/src/libmineziper_zip.c
+++ b/libmineziper/src/libmineziper_zip.c
@@ -62,8 +62,9 @@ void get_cdh(zip* z)
     z->lfh_off[i] = cdh->off_lfh;
     z->cdh_filename_length[i] = cdh->filename_length;
 
-    cdh = (CDH*) (((char*) cdh) + sizeof(CDH) + cdh->filename_length +
-                  cdh->extraf_length + cdh->file_comment_length);
+    unsigned short len = cdh->filename_length + cdh->extraf_length +
+                         cdh->file_comment_length;
+    cdh = (CDH*) (((char*) cdh) + sizeof(CDH) + len);
   }
 }