diff --git a/gcc/fortran/ChangeLog b/gcc/fortran/ChangeLog
index 4ae0e5b350a..29294f7e740 100644
--- a/gcc/fortran/ChangeLog
+++ b/gcc/fortran/ChangeLog
@@ -1,3 +1,9 @@
+2011-11-08  Francois-Xavier Coudert  <fxcoudert@gcc.gnu.org>
+
+	PR fortran/50409
+	* expr.c (gfc_simplify_expr): Substrings can't have negative
+	length.
+
 2011-11-08  Francois-Xavier Coudert  <fxcoudert@gcc.gnu.org>
 
 	PR fortran/50334
diff --git a/gcc/fortran/expr.c b/gcc/fortran/expr.c
index 504c7cf7d6b..f2414559653 100644
--- a/gcc/fortran/expr.c
+++ b/gcc/fortran/expr.c
@@ -1853,8 +1853,8 @@ gfc_simplify_expr (gfc_expr *p, int type)
 	  if (p->ref && p->ref->u.ss.end)
 	    gfc_extract_int (p->ref->u.ss.end, &end);
 
-	  if (end < 0)
-	    end = 0;
+	  if (end < start)
+	    end = start;
 
 	  s = gfc_get_wide_string (end - start + 2);
 	  memcpy (s, p->value.character.string + start,
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index b0cbbb6eb2e..de8cdc441a5 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2011-11-08  Francois-Xavier Coudert  <fxcoudert@gcc.gnu.org>
+
+	PR fortran/50409
+	* gcc/testsuite/gfortran.dg/string_5.f90: Improve testcase.
+
 2011-10-23  Jason Merrill  <jason@redhat.com>
 
 	PR c++/50835
diff --git a/gcc/testsuite/gfortran.dg/string_5.f90 b/gcc/testsuite/gfortran.dg/string_5.f90
index 87ec70942a5..ef291566b52 100644
--- a/gcc/testsuite/gfortran.dg/string_5.f90
+++ b/gcc/testsuite/gfortran.dg/string_5.f90
@@ -1,7 +1,14 @@
 ! { dg-do compile }
-! PR fortran/48876 - this used to segfault.
-! Test case contributed by mhp77 (a) gmx.at.
 program test
+
+  ! PR fortran/48876 - this used to segfault.
+  ! Test case contributed by mhp77 (a) gmx.at.
   character ::  string =  "string"( : -1 )
+
+  ! PR fortran/50409
+  character v(3)
+  v = (/ ('123'(i:1), i = 3, 1, -1) /) 
+  print *, v
+
 end program test