CRUNCH build failure on CHICKEN 6

This is on rev 5b1982d8.

~/.local/chicken-master/bin/chicken-install crunch
fetching crunch
building crunch

[...]

    /home/user/.local/chicken-master/bin/csc -host -D 
compiling-extension -J -s -regenerate-import-libraries -setup-mode -I 
/home/user/.cache/chicken-install/crunch -C 
-I/home/user/.cache/chicken-install/crunch -O2 -d1 crunch.scm -o 
/home/user/.cache/chicken-install/crunch/crunch.so
    /home/user/.local/chicken-master/bin/csc 
-regenerate-import-libraries -M -setup-mode -static -I 
/home/user/.cache/chicken-install/crunch -emit-link-file 
/home/user/.cache/chicken-install/crunch/crunch.link -host -D 
compiling-extension -c -unit crunch -D compiling-static-extension -C 
-I/home/user/.cache/chicken-install/crunch -O2 -d1 crunch.scm -o 
/home/user/.cache/chicken-install/crunch/crunch.static.o
    /home/user/.local/chicken-master/bin/csc -setup-mode -s -host -I 
/home/user/.cache/chicken-install/crunch -C 
-I/home/user/.cache/chicken-install/crunch -O2 -d0 crunch.import.scm -o 
/home/user/.cache/chicken-install/crunch/crunch.import.so
    /home/user/.local/chicken-master/bin/csc -setup-mode -host -I 
/home/user/.cache/chicken-install/crunch -C 
-I/home/user/.cache/chicken-install/crunch -O2 -d1 crunch-driver.scm -o 
/home/user/.cache/chicken-install/crunch/chicken-crunch

Error: Module `main' has unresolved identifiers
   In file `crunch-driver.scm':

   Unknown identifier `open-output-file'
     In procedure `failure851' on line 159
   Suggestion: try importing one of these modules:
     scheme.file
     scheme.r5rs
     scheme.r4rs

Error: shell command terminated with non-zero exit status 1: 
'/home/user/.local/chicken-master/bin/chicken' 'crunch-driver.scm' 
'-output-file' 
'/home/user/.cache/chicken-install/crunch/chicken-crunch.c' 
'-setup-mode' '-include-path' '/home/user/.cache/chicken-install/crunch' 
'-optimize-level' '2' '-debug-level' '1'

Error: shell command terminated with nonzero exit code
256
"sh /home/user/.cache/chicken-install/crunch/crunch.build.sh"

	Call history:

	egg-compile.scm:1183: ##sys#print	
	egg-compile.scm:1183: ##sys#print	
	egg-compile.scm:1183: ##sys#print	
	egg-compile.scm:1183: ##sys#print	
	egg-compile.scm:1183: ##sys#print	
	egg-compile.scm:1183: ##sys#write-char-0	
	chicken-install.scm:887: chicken.base#print	
	chicken-install.scm:888: run-script	
	chicken-install.scm:959: ##sys#get-keyword	
	chicken-install.scm:960: d	
	chicken-install.scm:967: chicken.platform#software-version	
	chicken-install.scm:963: scheme#string-append	
	chicken-install.scm:978: d	
	chicken-install.scm:979: system+	
	egg-compile.scm:1203: chicken.process#system	
	chicken-install.scm:982: chicken.base#error	 	<--