diff --git a/library/base64.c b/library/base64.c
index 8d49a81..8601c94 100644
--- a/library/base64.c
+++ b/library/base64.c
@@ -60,10 +60,10 @@
 /*
  * Encode a buffer into base64 format
  */
-int base64_encode( unsigned char *dst, int *dlen,
-                   const unsigned char *src, int  slen )
+int base64_encode( unsigned char *dst, size_t *dlen,
+                   const unsigned char *src, size_t slen )
 {
-    int i, n;
+    size_t i, n;
     int C1, C2, C3;
     unsigned char *p;
 
@@ -123,10 +123,10 @@
 /*
  * Decode a base64-formatted buffer
  */
-int base64_decode( unsigned char *dst, int *dlen,
-                   const unsigned char *src, int  slen )
+int base64_decode( unsigned char *dst, size_t *dlen,
+                   const unsigned char *src, size_t slen )
 {
-    int i, j, n;
+    size_t i, j, n;
     unsigned long x;
     unsigned char *p;
 
@@ -210,7 +210,7 @@
  */
 int base64_self_test( int verbose )
 {
-    int len;
+    size_t len;
     unsigned char *src, buffer[128];
 
     if( verbose != 0 )