diff --git a/basis/libc/libc.factor b/basis/libc/libc.factor
index 5495ec2705..a2ed34c267 100644
--- a/basis/libc/libc.factor
+++ b/basis/libc/libc.factor
@@ -24,16 +24,16 @@ FUNCTION-ALIAS: set-errno
 LIBRARY: libc
 
 FUNCTION-ALIAS: (malloc)
-    void* malloc ( ulong size ) ;
+    void* malloc ( size_t size ) ;
 
 FUNCTION-ALIAS: (calloc)
-    void* calloc ( ulong count,  ulong size ) ;
+    void* calloc ( size_t count,  size_t size ) ;
 
 FUNCTION-ALIAS: (free)
     void free ( void* alien ) ;
 
 FUNCTION-ALIAS: (realloc)
-    void* realloc ( void* alien, ulong size ) ;
+    void* realloc ( void* alien, size_t size ) ;
 
 <PRIVATE