diff --git a/guix/base64.scm b/guix/base64.scm
index 4bd5dc5e1b..0fa501eca0 100644
--- a/guix/base64.scm
+++ b/guix/base64.scm
@@ -5,6 +5,7 @@
 ;; February 12, 2014.
 ;;
 ;; Some optimizations made by Ludovic Courtès <ludo@gnu.org>, 2015.
+;; Turned into a Guile module (instead of R6RS).
 ;;
 ;; This program is free software: you can redistribute it and/or modify
 ;; it under the terms of the GNU General Public License as published by
@@ -42,211 +43,211 @@
 ;;   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 ;;   DEALINGS IN THE SOFTWARE.
 
-#!r6rs
-
 ;; RFC 4648 Base-N Encodings
 
-(library (guix base64)
-  (export base64-encode
-          base64-decode
-          base64-alphabet
-          base64url-alphabet
-          get-delimited-base64
-          put-delimited-base64)
-  (import (rnrs)
-          (only (srfi :13 strings)
-                string-index
-                string-prefix? string-suffix?
-                string-concatenate string-trim-both)
-          (only (guile) ash logior))
+(define-module (guix base64)
+  #:export (base64-encode
+            base64-decode
+            base64-alphabet
+            base64url-alphabet
+            get-delimited-base64
+            put-delimited-base64)
+  #:use-module (rnrs)
+  #:use-module ((srfi srfi-13)
+                #:select (string-index
+                          string-prefix? string-suffix?
+                          string-concatenate string-trim-both)))
 
 
-  (define-syntax define-alias
-    (syntax-rules ()
-      ((_ new old)
-       (define-syntax new (identifier-syntax old)))))
+(define-syntax define-alias
+  (syntax-rules ()
+    ((_ new old)
+     (define-syntax new (identifier-syntax old)))))
 
-  ;; Force the use of Guile's own primitives to avoid the overhead of its 'fx'
-  ;; procedures.
-  (define-alias fxbit-field bitwise-bit-field)
-  (define-alias fxarithmetic-shift ash)
-  (define-alias fxarithmetic-shift-left ash)
-  (define-alias fxand logand)
-  (define-alias fxior logior)
-  (define-alias fxxor logxor)
+;; Force the use of Guile's own primitives to avoid the overhead of its 'fx'
+;; procedures.
 
-  (define base64-alphabet
-    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/")
+(define-alias fxbit-field bitwise-bit-field)
+(define-alias fxarithmetic-shift ash)
+(define-alias fxarithmetic-shift-left ash)
+(define-alias fxand logand)
+(define-alias fxior logior)
+(define-alias fxxor logxor)
 
-  (define base64url-alphabet
-    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_")
+(define base64-alphabet
+  "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/")
 
-  (define base64-encode
-    (case-lambda
-      ;; Simple interface. Returns a string containing the canonical
-      ;; base64 representation of the given bytevector.
-      ((bv)
-       (base64-encode bv 0 (bytevector-length bv) #f #f base64-alphabet #f))
-      ((bv start)
-       (base64-encode bv start (bytevector-length bv) #f #f base64-alphabet #f))
-      ((bv start end)
-       (base64-encode bv start end #f #f base64-alphabet #f))
-      ((bv start end line-length)
-       (base64-encode bv start end line-length #f base64-alphabet #f))
-      ((bv start end line-length no-padding)
-       (base64-encode bv start end line-length no-padding base64-alphabet #f))
-      ((bv start end line-length no-padding alphabet)
-       (base64-encode bv start end line-length no-padding alphabet #f))
-      ;; Base64 encodes the bytes [start,end[ in the given bytevector.
-      ;; Lines are limited to line-length characters (unless #f),
-      ;; which must be a multiple of four. To omit the padding
-      ;; characters (#\=) set no-padding to a true value. If port is
-      ;; #f, returns a string.
-      ((bv start end line-length no-padding alphabet port)
-       (assert (or (not line-length) (zero? (mod line-length 4))))
-       (let-values (((p extract) (if port
-                                     (values port (lambda () (values)))
-                                     (open-string-output-port))))
-         (letrec ((put (if line-length
-                           (let ((chars 0))
-                             (lambda (p c)
-                               (when (fx=? chars line-length)
-                                 (set! chars 0)
-                                 (put-char p #\linefeed))
-                               (set! chars (fx+ chars 1))
-                               (put-char p c)))
-                           put-char)))
-           (let lp ((i start))
-             (cond ((= i end))
-                   ((<= (+ i 3) end)
-                    (let ((x (bytevector-uint-ref bv i (endianness big) 3)))
-                      (put p (string-ref alphabet (fxbit-field x 18 24)))
-                      (put p (string-ref alphabet (fxbit-field x 12 18)))
-                      (put p (string-ref alphabet (fxbit-field x 6 12)))
-                      (put p (string-ref alphabet (fxbit-field x 0 6)))
-                      (lp (+ i 3))))
-                   ((<= (+ i 2) end)
-                    (let ((x (fxarithmetic-shift-left (bytevector-u16-ref bv i (endianness big)) 8)))
-                      (put p (string-ref alphabet (fxbit-field x 18 24)))
-                      (put p (string-ref alphabet (fxbit-field x 12 18)))
-                      (put p (string-ref alphabet (fxbit-field x 6 12)))
-                      (unless no-padding
-                        (put p #\=))))
-                   (else
-                    (let ((x (fxarithmetic-shift-left (bytevector-u8-ref bv i) 16)))
-                      (put p (string-ref alphabet (fxbit-field x 18 24)))
-                      (put p (string-ref alphabet (fxbit-field x 12 18)))
-                      (unless no-padding
-                        (put p #\=)
-                        (put p #\=)))))))
-         (extract)))))
+(define base64url-alphabet
+  "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_")
+
+(define base64-encode
+  (case-lambda
+    ;; Simple interface. Returns a string containing the canonical
+    ;; base64 representation of the given bytevector.
+    ((bv)
+     (base64-encode bv 0 (bytevector-length bv) #f #f base64-alphabet #f))
+    ((bv start)
+     (base64-encode bv start (bytevector-length bv) #f #f base64-alphabet #f))
+    ((bv start end)
+     (base64-encode bv start end #f #f base64-alphabet #f))
+    ((bv start end line-length)
+     (base64-encode bv start end line-length #f base64-alphabet #f))
+    ((bv start end line-length no-padding)
+     (base64-encode bv start end line-length no-padding base64-alphabet #f))
+    ((bv start end line-length no-padding alphabet)
+     (base64-encode bv start end line-length no-padding alphabet #f))
+    ;; Base64 encodes the bytes [start,end[ in the given bytevector.
+    ;; Lines are limited to line-length characters (unless #f),
+    ;; which must be a multiple of four. To omit the padding
+    ;; characters (#\=) set no-padding to a true value. If port is
+    ;; #f, returns a string.
+    ((bv start end line-length no-padding alphabet port)
+     (assert (or (not line-length) (zero? (mod line-length 4))))
+     (let-values (((p extract) (if port
+                                   (values port (lambda () (values)))
+                                   (open-string-output-port))))
+       (letrec ((put (if line-length
+                         (let ((chars 0))
+                           (lambda (p c)
+                             (when (fx=? chars line-length)
+                               (set! chars 0)
+                               (put-char p #\linefeed))
+                             (set! chars (fx+ chars 1))
+                             (put-char p c)))
+                         put-char)))
+         (let lp ((i start))
+           (cond ((= i end))
+                 ((<= (+ i 3) end)
+                  (let ((x (bytevector-uint-ref bv i (endianness big) 3)))
+                    (put p (string-ref alphabet (fxbit-field x 18 24)))
+                    (put p (string-ref alphabet (fxbit-field x 12 18)))
+                    (put p (string-ref alphabet (fxbit-field x 6 12)))
+                    (put p (string-ref alphabet (fxbit-field x 0 6)))
+                    (lp (+ i 3))))
+                 ((<= (+ i 2) end)
+                  (let ((x (fxarithmetic-shift-left (bytevector-u16-ref bv i (endianness big)) 8)))
+                    (put p (string-ref alphabet (fxbit-field x 18 24)))
+                    (put p (string-ref alphabet (fxbit-field x 12 18)))
+                    (put p (string-ref alphabet (fxbit-field x 6 12)))
+                    (unless no-padding
+                      (put p #\=))))
+                 (else
+                  (let ((x (fxarithmetic-shift-left (bytevector-u8-ref bv i) 16)))
+                    (put p (string-ref alphabet (fxbit-field x 18 24)))
+                    (put p (string-ref alphabet (fxbit-field x 12 18)))
+                    (unless no-padding
+                      (put p #\=)
+                      (put p #\=)))))))
+       (extract)))))
 
   ;; Decodes a base64 string. The string must contain only pure
   ;; unpadded base64 data.
-  (define base64-decode
-    (case-lambda
-      ((str)
-       (base64-decode str base64-alphabet #f))
-      ((str alphabet)
-       (base64-decode str alphabet #f))
-      ((str alphabet port)
-       (unless (zero? (mod (string-length str) 4))
-         (error 'base64-decode
-                "input string must be a multiple of four characters"))
-       (let-values (((p extract) (if port
-                                     (values port (lambda () (values)))
-                                     (open-bytevector-output-port))))
-         (do ((i 0 (+ i 4)))
-             ((= i (string-length str))
-              (extract))
-           (let ((c1 (string-ref str i))
-                 (c2 (string-ref str (+ i 1)))
-                 (c3 (string-ref str (+ i 2)))
-                 (c4 (string-ref str (+ i 3))))
-             ;; TODO: be more clever than string-index
-             (let ((i1 (string-index alphabet c1))
-                   (i2 (string-index alphabet c2))
-                   (i3 (string-index alphabet c3))
-                   (i4 (string-index alphabet c4)))
-               (cond ((and i1 i2 i3 i4)
-                      (let ((x (fxior (fxarithmetic-shift-left i1 18)
-                                      (fxarithmetic-shift-left i2 12)
-                                      (fxarithmetic-shift-left i3 6)
-                                      i4)))
-                        (put-u8 p (fxbit-field x 16 24))
-                        (put-u8 p (fxbit-field x 8 16))
-                        (put-u8 p (fxbit-field x 0 8))))
-                     ((and i1 i2 i3 (char=? c4 #\=)
-                           (= i (- (string-length str) 4)))
-                      (let ((x (fxior (fxarithmetic-shift-left i1 18)
-                                      (fxarithmetic-shift-left i2 12)
-                                      (fxarithmetic-shift-left i3 6))))
-                        (put-u8 p (fxbit-field x 16 24))
-                        (put-u8 p (fxbit-field x 8 16))))
-                     ((and i1 i2 (char=? c3 #\=) (char=? c4 #\=)
-                           (= i (- (string-length str) 4)))
-                      (let ((x (fxior (fxarithmetic-shift-left i1 18)
-                                      (fxarithmetic-shift-left i2 12))))
-                        (put-u8 p (fxbit-field x 16 24))))
-                     (else
-                      (error 'base64-decode "invalid input"
-                             (list c1 c2 c3 c4)))))))))))
+  
+(define base64-decode
+  (case-lambda
+    ((str)
+     (base64-decode str base64-alphabet #f))
+    ((str alphabet)
+     (base64-decode str alphabet #f))
+    ((str alphabet port)
+     (unless (zero? (mod (string-length str) 4))
+       (error 'base64-decode
+              "input string must be a multiple of four characters"))
+     (let-values (((p extract) (if port
+                                   (values port (lambda () (values)))
+                                   (open-bytevector-output-port))))
+       (do ((i 0 (+ i 4)))
+           ((= i (string-length str))
+            (extract))
+         (let ((c1 (string-ref str i))
+               (c2 (string-ref str (+ i 1)))
+               (c3 (string-ref str (+ i 2)))
+               (c4 (string-ref str (+ i 3))))
+           ;; TODO: be more clever than string-index
+           (let ((i1 (string-index alphabet c1))
+                 (i2 (string-index alphabet c2))
+                 (i3 (string-index alphabet c3))
+                 (i4 (string-index alphabet c4)))
+             (cond ((and i1 i2 i3 i4)
+                    (let ((x (fxior (fxarithmetic-shift-left i1 18)
+                                    (fxarithmetic-shift-left i2 12)
+                                    (fxarithmetic-shift-left i3 6)
+                                    i4)))
+                      (put-u8 p (fxbit-field x 16 24))
+                      (put-u8 p (fxbit-field x 8 16))
+                      (put-u8 p (fxbit-field x 0 8))))
+                   ((and i1 i2 i3 (char=? c4 #\=)
+                         (= i (- (string-length str) 4)))
+                    (let ((x (fxior (fxarithmetic-shift-left i1 18)
+                                    (fxarithmetic-shift-left i2 12)
+                                    (fxarithmetic-shift-left i3 6))))
+                      (put-u8 p (fxbit-field x 16 24))
+                      (put-u8 p (fxbit-field x 8 16))))
+                   ((and i1 i2 (char=? c3 #\=) (char=? c4 #\=)
+                         (= i (- (string-length str) 4)))
+                    (let ((x (fxior (fxarithmetic-shift-left i1 18)
+                                    (fxarithmetic-shift-left i2 12))))
+                      (put-u8 p (fxbit-field x 16 24))))
+                   (else
+                    (error 'base64-decode "invalid input"
+                           (list c1 c2 c3 c4)))))))))))
 
-  (define (get-line-comp f port)
-    (if (port-eof? port)
-        (eof-object)
-        (f (get-line port))))
+(define (get-line-comp f port)
+  (if (port-eof? port)
+      (eof-object)
+      (f (get-line port))))
 
   ;; Reads the common -----BEGIN/END type----- delimited format from
   ;; the given port. Returns two values: a string with the type and a
   ;; bytevector containing the base64 decoded data. The second value
   ;; is the eof object if there is an eof before the BEGIN delimiter.
-  (define (get-delimited-base64 port)
-    (define (get-first-data-line port)
-      ;; Some MIME data has header fields in the same format as mail
-      ;; or http. These are ignored.
-      (let ((line (get-line-comp string-trim-both port)))
-        (cond ((eof-object? line) line)
-              ((string-index line #\:)
-               (let lp ()               ;read until empty line
-                 (let ((line (get-line-comp string-trim-both port)))
-                   (if (string=? line "")
-                       (get-line-comp string-trim-both port)
-                       (lp)))))
-              (else line))))
+  
+(define (get-delimited-base64 port)
+  (define (get-first-data-line port)
+    ;; Some MIME data has header fields in the same format as mail
+    ;; or http. These are ignored.
     (let ((line (get-line-comp string-trim-both port)))
-      (cond ((eof-object? line)
-             (values "" (eof-object)))
-            ((string=? line "")
-             (get-delimited-base64 port))
-            ((and (string-prefix? "-----BEGIN " line)
-                  (string-suffix? "-----" line))
-             (let* ((type (substring line 11 (- (string-length line) 5)))
-                    (endline (string-append "-----END " type "-----")))
-               (let-values (((outp extract) (open-bytevector-output-port)))
-                 (let lp ((line (get-first-data-line port)))
-                   (cond ((eof-object? line)
+      (cond ((eof-object? line) line)
+            ((string-index line #\:)
+             (let lp ()                           ;read until empty line
+               (let ((line (get-line-comp string-trim-both port)))
+                 (if (string=? line "")
+                     (get-line-comp string-trim-both port)
+                     (lp)))))
+            (else line))))
+  (let ((line (get-line-comp string-trim-both port)))
+    (cond ((eof-object? line)
+           (values "" (eof-object)))
+          ((string=? line "")
+           (get-delimited-base64 port))
+          ((and (string-prefix? "-----BEGIN " line)
+                (string-suffix? "-----" line))
+           (let* ((type (substring line 11 (- (string-length line) 5)))
+                  (endline (string-append "-----END " type "-----")))
+             (let-values (((outp extract) (open-bytevector-output-port)))
+               (let lp ((line (get-first-data-line port)))
+                 (cond ((eof-object? line)
+                        (error 'get-delimited-base64
+                               "unexpected end of file"))
+                       ((string-prefix? "-" line)
+                        (unless (string=? line endline)
                           (error 'get-delimited-base64
-                                 "unexpected end of file"))
-                         ((string-prefix? "-" line)
-                          (unless (string=? line endline)
-                            (error 'get-delimited-base64
-                                   "bad end delimiter" type line))
-                          (values type (extract)))
-                         (else
-                          (unless (and (= (string-length line) 5)
-                                       (string-prefix? "=" line)) ;Skip Radix-64 checksum
-                            (base64-decode line base64-alphabet outp))
-                          (lp (get-line-comp string-trim-both port))))))))
-            (else ;skip garbage (like in openssl x509 -in foo -text output).
-             (get-delimited-base64 port)))))
+                                 "bad end delimiter" type line))
+                        (values type (extract)))
+                       (else
+                        (unless (and (= (string-length line) 5)
+                                     (string-prefix? "=" line)) ;Skip Radix-64 checksum
+                          (base64-decode line base64-alphabet outp))
+                        (lp (get-line-comp string-trim-both port))))))))
+          (else     ;skip garbage (like in openssl x509 -in foo -text output).
+           (get-delimited-base64 port)))))
 
-  (define put-delimited-base64
-    (case-lambda
-      ((port type bv line-length)
-       (display (string-append "-----BEGIN " type "-----\n") port)
-       (base64-encode bv 0 (bytevector-length bv)
-                      line-length #f base64-alphabet port)
-       (display (string-append "\n-----END " type "-----\n") port))
-      ((port type bv)
-       (put-delimited-base64 port type bv 76)))))
+(define put-delimited-base64
+  (case-lambda
+    ((port type bv line-length)
+     (display (string-append "-----BEGIN " type "-----\n") port)
+     (base64-encode bv 0 (bytevector-length bv)
+                    line-length #f base64-alphabet port)
+     (display (string-append "\n-----END " type "-----\n") port))
+    ((port type bv)
+     (put-delimited-base64 port type bv 76))))