Index: fortran/scanner.c
===================================================================
--- fortran/scanner.c	(Revision 189754)
+++ fortran/scanner.c	(Arbeitskopie)
@@ -311,12 +311,30 @@ add_path_to_list (gfc_directorylist **list, const
 {
   gfc_directorylist *dir;
   const char *p;
-
+  struct stat st;
+  
   p = path;
   while (*p == ' ' || *p == '\t')  /* someone might do "-I include" */
     if (*p++ == '\0')
       return;
 
+  if (stat (p, &st))
+    {
+      if (errno != ENOENT)
+	gfc_warning_now ("Include directory \"%s\": %s", path,
+			 xstrerror(errno));
+      else
+	/* FIXME:  Also support -Wmissing-include-dirs.  */
+	gfc_warning_now ("Nonexistent include directory \"%s\"", path);
+      return;
+    }
+
+  else if (!S_ISDIR (st.st_mode))
+    {
+      gfc_warning_now ("\"%s\" is not a directory", path);
+      return;
+    }
+
   if (head || *list == NULL)
     {
       dir = XCNEW (gfc_directorylist);
Index: testsuite/gfortran.dg/include_3.f95
===================================================================
--- testsuite/gfortran.dg/include_3.f95	(Revision 189754)
+++ testsuite/gfortran.dg/include_3.f95	(Arbeitskopie)
@@ -24,3 +24,4 @@ end function
 
 ! { dg-do compile }
 ! { dg-options "-fpreprocessed -g3" }
+! { dg-warning "Nonexistent include directory" "missing directory" { target *-*-* } 0 }