diff --git a/libcpp/ChangeLog b/libcpp/ChangeLog
index 7365c4e7beb7..07ef24378345 100644
--- a/libcpp/ChangeLog
+++ b/libcpp/ChangeLog
@@ -1,3 +1,7 @@
+2012-05-10  Tristan Gingold  <gingold@adacore.com>
+
+	* expr.c (interpret_float_suffix): Add a guard.
+
 2012-05-02  Dodji Seketeli  <dodji@redhat.com>
 
 	Properly initialize cpp_context in destringize_and_run
diff --git a/libcpp/expr.c b/libcpp/expr.c
index d56e56a63111..ca1c3d1928a9 100644
--- a/libcpp/expr.c
+++ b/libcpp/expr.c
@@ -110,12 +110,13 @@ interpret_float_suffix (const uchar *s, size_t len)
     }
 
   /* Recognize a fixed-point suffix.  */
-  switch (s[len-1])
-    {
-    case 'k': case 'K': flags = CPP_N_ACCUM; break;
-    case 'r': case 'R': flags = CPP_N_FRACT; break;
-    default: break;
-    }
+  if (len != 0)
+    switch (s[len-1])
+      {
+      case 'k': case 'K': flags = CPP_N_ACCUM; break;
+      case 'r': case 'R': flags = CPP_N_FRACT; break;
+      default: break;
+      }
 
   /* Continue processing a fixed-point suffix.  The suffix is case
      insensitive except for ll or LL.  Order is significant.  */