diff --git a/gnu/packages/maths.scm b/gnu/packages/maths.scm
index e3d3216eab..08e0e7dd7a 100644
--- a/gnu/packages/maths.scm
+++ b/gnu/packages/maths.scm
@@ -4863,6 +4863,18 @@ This package contains the basic DUNE grid classes.")
     (arguments
      `(#:phases
        (modify-phases %standard-phases
+         ;; XXX: istl/test/matrixtest.cc includes <fenv.h> and fails to find
+         ;; the stdlib types when the gfortran header is used.  Remove gfortran
+         ;; from CPLUS_INCLUDE_PATH as a workaround.
+         (add-after 'set-paths 'hide-gfortran
+           (lambda* (#:key inputs #:allow-other-keys)
+             (let ((gfortran (assoc-ref inputs "gfortran")))
+               (setenv "CPLUS_INCLUDE_PATH"
+                       (string-join
+                        (delete (string-append gfortran "/include/c++")
+                                (string-split (getenv "CPLUS_INCLUDE_PATH") #\:))
+                        ":"))
+               #t)))
          (add-after 'build 'build-tests
            (lambda* (#:key make-flags #:allow-other-keys)
              (apply invoke "make" "build_tests" make-flags))))))