diff --git a/src/flex.skl b/src/flex.skl
index 18501d5..ae60559 100644
--- a/src/flex.skl
+++ b/src/flex.skl
@@ -1782,7 +1782,7 @@ m4_ifdef( [[M4_YY_USES_REJECT]],
 		/* Extend the array by 50%, plus the number we really need. */
 		int new_size = YY_G(yy_n_chars) + number_to_move + (YY_G(yy_n_chars) >> 1);
 		YY_CURRENT_BUFFER_LVALUE->yy_ch_buf = (char *) yyrealloc(
-			(void *) YY_CURRENT_BUFFER_LVALUE->yy_ch_buf, new_size M4_YY_CALL_LAST_ARG );
+			(void *) YY_CURRENT_BUFFER_LVALUE->yy_ch_buf, (yy_size_t) new_size M4_YY_CALL_LAST_ARG );
 		if ( ! YY_CURRENT_BUFFER_LVALUE->yy_ch_buf )
 			YY_FATAL_ERROR( "out of dynamic memory in yy_get_next_buffer()" );
 	}