diff --git a/core/io/io.factor b/core/io/io.factor
index 6bad8331db..522e767f98 100755
--- a/core/io/io.factor
+++ b/core/io/io.factor
@@ -39,6 +39,7 @@ SYMBOL: error-stream
 : read1 ( -- ch/f ) input-stream get stream-read1 ;
 : read ( n -- str/f ) input-stream get stream-read ;
 : read-until ( seps -- str/f sep/f ) input-stream get stream-read-until ;
+: read-partial ( n -- str/f ) input-stream get stream-read-partial ;
 
 : write1 ( ch -- ) output-stream get stream-write1 ;
 : write ( str -- ) output-stream get stream-write ;