diff --git a/extmod/uzlib/tinf.h b/extmod/uzlib/tinf.h
index d82959df98..e9401f2de5 100644
--- a/extmod/uzlib/tinf.h
+++ b/extmod/uzlib/tinf.h
@@ -76,7 +76,7 @@ int TINFCC tinf_zlib_uncompress_dyn(TINF_DATA *d, unsigned int sourceLen);
 
 /* high-level API */
 
-void TINFCC tinf_init();
+void TINFCC tinf_init(void);
 
 int TINFCC tinf_uncompress(void *dest, unsigned int *destLen,
                            const void *source, unsigned int sourceLen);
diff --git a/extmod/uzlib/tinflate.c b/extmod/uzlib/tinflate.c
index d5197a590e..74b1bc30f3 100644
--- a/extmod/uzlib/tinflate.c
+++ b/extmod/uzlib/tinflate.c
@@ -341,8 +341,8 @@ static int tinf_inflate_block_data(TINF_DATA *d, TINF_TREE *lt, TINF_TREE *dt)
 
       } else {
 
-         int length, dist, offs;
-         int i;
+         unsigned int length, offs, i;
+         int dist;
 
          sym -= 257;
 
@@ -363,7 +363,7 @@ static int tinf_inflate_block_data(TINF_DATA *d, TINF_TREE *lt, TINF_TREE *dt)
          /* copy match */
          for (i = 0; i < length; ++i)
          {
-            d->dest[i] = d->dest[i - offs];
+            d->dest[i] = d->dest[(int)(i - offs)];
          }
 
          d->dest += length;
@@ -432,7 +432,7 @@ static int tinf_inflate_dynamic_block(TINF_DATA *d)
  * ---------------------- */
 
 /* initialize global (static) data */
-void tinf_init()
+void tinf_init(void)
 {
 #ifdef RUNTIME_BITS_TABLES
    /* build extra bits and base tables */
@@ -449,6 +449,7 @@ void tinf_init()
 int tinf_uncompress(void *dest, unsigned int *destLen,
                     const void *source, unsigned int sourceLen)
 {
+   (void)sourceLen;
    TINF_DATA d;
    int res;