diff --git a/third_party/gmp/invalid.c b/third_party/gmp/invalid.c
new file mode 100644
index 0000000..e09eab2
--- /dev/null
+++ b/third_party/gmp/invalid.c
@@ -0,0 +1,82 @@
+/* __gmp_invalid_operation -- invalid floating point operation.
+
+   THE FUNCTIONS IN THIS FILE ARE FOR INTERNAL USE ONLY.  THEY'RE ALMOST
+   CERTAIN TO BE SUBJECT TO INCOMPATIBLE CHANGES OR DISAPPEAR COMPLETELY IN
+   FUTURE GNU MP RELEASES.
+
+Copyright 2003 Free Software Foundation, Inc.
+
+This file is part of the GNU MP Library.
+
+The GNU MP Library is free software; you can redistribute it and/or modify
+it under the terms of either:
+
+  * the GNU Lesser General Public License as published by the Free
+    Software Foundation; either version 3 of the License, or (at your
+    option) any later version.
+
+or
+
+  * the GNU General Public License as published by the Free Software
+    Foundation; either version 2 of the License, or (at your option) any
+    later version.
+
+or both in parallel, as here.
+
+The GNU MP Library is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received copies of the GNU General Public License and the
+GNU Lesser General Public License along with the GNU MP Library.  If not,
+see https://www.gnu.org/licenses/.  */
+
+#include "config.h"
+
+#include <signal.h>
+#include <stdlib.h>
+
+#if HAVE_UNISTD_H
+#include <unistd.h>  /* for getpid */
+#endif
+
+#include "gmp-impl.h"
+
+
+/* Incidentally, kill is not available on mingw, but that's ok, it has raise
+   and we'll be using that.  */
+#if ! HAVE_RAISE
+#define raise(sig)   kill (getpid(), sig)
+#endif
+
+
+/* __gmp_invalid_operation is for an invalid floating point operation, like
+   mpz_set_d on a NaN or Inf.  It's done as a subroutine to minimize code in
+   places raising an exception.
+
+   feraiseexcept(FE_INVALID) is not used here, since unfortunately on most
+   systems it would require libm.
+
+   Alternatives:
+
+   It might be possible to check whether a hardware "invalid operation" trap
+   is enabled or not before raising a signal.  This would require all
+   callers to be prepared to continue with some bogus result.  Bogus returns
+   are bad, but presumably an application disabling the trap is prepared for
+   that.
+
+   On some systems (eg. BSD) the signal handler can find out the reason for
+   a SIGFPE (overflow, invalid, div-by-zero, etc).  Perhaps we could get
+   that into our raise too.
+
+   i386 GLIBC implements feraiseexcept(FE_INVALID) with an asm fdiv 0/0.
+   That would both respect the exceptions mask and give a reason code in a
+   BSD signal.  */
+
+void
+__gmp_invalid_operation (void)
+{
+  raise (SIGFPE);
+  abort ();
+}