diff --git a/guix/build-system/cmake.scm b/guix/build-system/cmake.scm
index 5673ad5aeb..5e7fba0ac3 100644
--- a/guix/build-system/cmake.scm
+++ b/guix/build-system/cmake.scm
@@ -98,8 +98,6 @@ provides a 'CMakeLists.txt' file as its build system."
     (match guile
       ((? package?)
        (package-derivation store guile system))
-      ((and (? string?) (? derivation-path?))
-       guile)
       (#f                                         ; the default
        (let* ((distro (resolve-interface '(gnu packages commencement)))
               (guile  (module-ref distro 'guile-final)))
diff --git a/guix/build-system/gnu.scm b/guix/build-system/gnu.scm
index 7c9b6ca398..372ad14b71 100644
--- a/guix/build-system/gnu.scm
+++ b/guix/build-system/gnu.scm
@@ -344,8 +344,6 @@ are allowed to refer to."
     (match guile
       ((? package?)
        (package-derivation store guile system))
-      ;; ((and (? string?) (? derivation-path?))
-      ;;  guile)
       (#f                                         ; the default
        (let* ((distro (resolve-interface '(gnu packages commencement)))
               (guile  (module-ref distro 'guile-final)))
@@ -530,8 +528,6 @@ platform."
     (match guile
       ((? package?)
        (package-derivation store guile system))
-      ;; ((and (? string?) (? derivation-path?))
-      ;;  guile)
       (#f                                         ; the default
        (let* ((distro (resolve-interface '(gnu packages commencement)))
               (guile  (module-ref distro 'guile-final)))
diff --git a/guix/build-system/perl.scm b/guix/build-system/perl.scm
index 993cd7448e..600e597ce8 100644
--- a/guix/build-system/perl.scm
+++ b/guix/build-system/perl.scm
@@ -90,8 +90,6 @@ provides a `Makefile.PL' file as its build system."
     (match guile
       ((? package?)
        (package-derivation store guile system))
-      ((and (? string?) (? derivation-path?))
-       guile)
       (#f                                         ; the default
        (let* ((distro (resolve-interface '(gnu packages commencement)))
               (guile  (module-ref distro 'guile-final)))
diff --git a/guix/build-system/python.scm b/guix/build-system/python.scm
index dfb8b4a137..a90e7ff511 100644
--- a/guix/build-system/python.scm
+++ b/guix/build-system/python.scm
@@ -138,8 +138,6 @@ provides a 'setup.py' file as its build system."
     (match guile
       ((? package?)
        (package-derivation store guile system))
-      ((and (? string?) (? derivation-path?))
-       guile)
       (#f                                         ; the default
        (let* ((distro (resolve-interface '(gnu packages commencement)))
               (guile  (module-ref distro 'guile-final)))
diff --git a/guix/build-system/ruby.scm b/guix/build-system/ruby.scm
index f20967a619..426ca3718c 100644
--- a/guix/build-system/ruby.scm
+++ b/guix/build-system/ruby.scm
@@ -77,8 +77,6 @@
     (match guile
       ((? package?)
        (package-derivation store guile system))
-      ((and (? string?) (? derivation-path?))
-       guile)
       (#f
        (let* ((distro (resolve-interface '(gnu packages commencement)))
               (guile  (module-ref distro 'guile-final)))
diff --git a/guix/build-system/trivial.scm b/guix/build-system/trivial.scm
index 475e8563e5..897c5c6152 100644
--- a/guix/build-system/trivial.scm
+++ b/guix/build-system/trivial.scm
@@ -29,8 +29,6 @@
   (match guile
     ((? package?)
      (package-derivation store guile system))
-    ((and (? string?) (? derivation-path?))
-     guile)
     (#f                                         ; the default
      (let* ((distro (resolve-interface '(gnu packages commencement)))
             (guile  (module-ref distro 'guile-final)))