Problem testing cond-expand syntax from (scheme base) in pure module

[Maxim Cournoyer <maxim.cournoyer@gmail.com>]

Hello,

I'm trying to test cond-expand as provided by (scheme base), which is
the R7RS flavored version of cond-expand, but it fails when in a pure
Guile module:

--8<---------------cut here---------------start------------->8---
new file   test-suite/tests/r7rs-cond-expand.test
@@ -0,0 +1,19 @@
+(define-module (test-suite r7rs-cond-expand)
+  #:pure
+  #:use-module (scheme base)
+  #:use-module ((srfi srfi-64) #:select (test-read-eval-string))
+  #:use-module (test-suite lib))
+
+(pass-if "cond-expand expression missing library test"
+  (test-read-eval-string "\
+(cond-expand
+ ((library (srfi srfi-99999))
+  #f)
+ (else #t))"))
+
+(pass-if "cond-expand expression found library test"
+  (test-read-eval-string "\
+(cond-expand
+ ((library (srfi srfi-64))
+  #t)
+ (else #f))"))

# Running it:
./meta/guile -L test-suite -L . test-suite/tests/r7rs-cond-expand.test
ERROR: cond-expand expression missing library test - arguments: ((syntax-error #f "source expression failed to match any pattern" ((line . 1) (column . 2)) (library (srfi srfi-99999)) #f))
ERROR: cond-expand expression found library test - arguments: ((syntax-error #f "source expression failed to match any pattern" ((line . 1) (column . 2)) (library (srfi srfi-64)) #f))
--8<---------------cut here---------------end--------------->8---

Would someone have a clue as to why?

If I drop #:pure, it then works as expected.  Is this a bug?

-- 
Thanks,
Maxim