diff --git a/hiredis.c b/hiredis.c
index 66789d0..ffdf027 100644
--- a/hiredis.c
+++ b/hiredis.c
@@ -424,7 +424,7 @@ char *redisReplyReaderGetError(void *reader) {
     return r->error;
 }
 
-void redisReplyReaderFeed(void *reader, char *buf, int len) {
+void redisReplyReaderFeed(void *reader, char *buf, size_t len) {
     redisReader *r = reader;
 
     /* Copy the provided buffer. */
diff --git a/hiredis.h b/hiredis.h
index 0a6a9a1..cb25b36 100644
--- a/hiredis.h
+++ b/hiredis.h
@@ -115,7 +115,7 @@ int redisReplyReaderSetReplyObjectFunctions(void *reader, redisReplyObjectFuncti
 void *redisReplyReaderGetObject(void *reader);
 char *redisReplyReaderGetError(void *reader);
 void redisReplyReaderFree(void *ptr);
-void redisReplyReaderFeed(void *reader, char *buf, int len);
+void redisReplyReaderFeed(void *reader, char *buf, size_t len);
 int redisReplyReaderGetReply(void *reader, void **reply);
 
 /* Functions to format a command according to the protocol. */