diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 4d30efb3dae3..b6714aa40b26 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2005-03-31  Francois-Xavier Coudert  <coudert@clipper.ens.fr>
+
+	PR libfortran/20660
+	* gfortran.dg/negative_unit.f: New test.
+
 2005-03-31 Mostafa Hagog <mustafa@il.ibm.com>
 
 	* gcc.dg/20050330-1.c: New test.
diff --git a/gcc/testsuite/gfortran.dg/negative_unit.f b/gcc/testsuite/gfortran.dg/negative_unit.f
new file mode 100644
index 000000000000..ba0d3cd1a4d1
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/negative_unit.f
@@ -0,0 +1,22 @@
+! {dg-do run}
+!
+! PR libfortran/20660 and other bugs (not filed in bugzilla) relating
+! to negative units
+!
+! Bugs submitted by Walt Brainerd
+      integer i
+      logical l
+      
+      i = 0
+! gfortran created a 'fort.-1' file and wrote "Hello" in it
+      write (unit=-1, fmt=*, iostat=i) "Hello"
+      if (i <= 0) call abort
+      
+      i = 0
+      open (unit=-11, file="xxx", iostat=i)
+      if (i <= 0) call abort
+
+      inquire (unit=-42, exist=l)
+      if (l) call abort
+
+      end
diff --git a/libgfortran/ChangeLog b/libgfortran/ChangeLog
index edc23af6ce93..027263899d08 100644
--- a/libgfortran/ChangeLog
+++ b/libgfortran/ChangeLog
@@ -1,3 +1,10 @@
+2005-03-31  Francois-Xavier Coudert  <coudert@clipper.ens.fr>
+
+	PR libfortran/20660
+	* io/inquire.c (inquire_via_unit): Non-opened units should still be
+	reported by an INQUIRE statement as existing.
+	* io/transfer.c (data_transfer_init): Never accept negative units.
+
 2005-03-29  Dale Ranta  <dir@lanl.gov>
 	    Francois-Xavier Coudert  <coudert@clipper.ens.fr>
 
diff --git a/libgfortran/io/inquire.c b/libgfortran/io/inquire.c
index 28c2f6afbc5c..1f0fcac6530f 100644
--- a/libgfortran/io/inquire.c
+++ b/libgfortran/io/inquire.c
@@ -46,7 +46,12 @@ inquire_via_unit (gfc_unit * u)
   const char *p;
 
   if (ioparm.exist != NULL)
-    *ioparm.exist = (u != NULL);
+  {
+    if (ioparm.unit >= 0)
+      *ioparm.exist = 1;
+    else
+      *ioparm.exist = 0;
+  }
 
   if (ioparm.opened != NULL)
     *ioparm.opened = (u != NULL);
diff --git a/libgfortran/io/transfer.c b/libgfortran/io/transfer.c
index aed0aa90dbc8..4d4832395d95 100644
--- a/libgfortran/io/transfer.c
+++ b/libgfortran/io/transfer.c
@@ -935,6 +935,12 @@ data_transfer_init (int read_flag)
   current_unit = get_unit (read_flag);
   if (current_unit == NULL)
   {  /* Open the unit with some default flags.  */
+     if (ioparm.unit < 0)
+     {
+       generate_error (ERROR_BAD_OPTION, "Bad unit number in OPEN statement");
+       library_end ();
+       return;
+     }
      memset (&u_flags, '\0', sizeof (u_flags));
      u_flags.access = ACCESS_SEQUENTIAL;
      u_flags.action = ACTION_READWRITE;