diff --git a/libbacktrace/ChangeLog b/libbacktrace/ChangeLog
index 4850d9de37bd..f04f1d5dd0dd 100644
--- a/libbacktrace/ChangeLog
+++ b/libbacktrace/ChangeLog
@@ -1,3 +1,8 @@
+2012-10-29  Ian Lance Taylor  <iant@google.com>
+
+	* mmap.c (backtrace_vector_release): Make sure freed block is
+	aligned on 8-byte boundary.
+
 2012-10-26  Ian Lance Taylor  <iant@google.com>
 
 	PR other/55087
diff --git a/libbacktrace/mmap.c b/libbacktrace/mmap.c
index e07810d4575e..25fdc21a9f7e 100644
--- a/libbacktrace/mmap.c
+++ b/libbacktrace/mmap.c
@@ -229,8 +229,18 @@ backtrace_vector_release (struct backtrace_state *state,
 			  backtrace_error_callback error_callback,
 			  void *data)
 {
-  backtrace_free (state, (char *) vec->base + vec->size, vec->alc,
-		  error_callback, data);
+  size_t size;
+  size_t alc;
+  size_t aligned;
+
+  /* Make sure that the block that we free is aligned on an 8-byte
+     boundary.  */
+  size = vec->size;
+  alc = vec->alc;
+  aligned = (size + 7) & ~ (size_t) 7;
+  alc -= aligned - size;
+
+  backtrace_free (state, (char *) vec->base + size, alc, error_callback, data);
   vec->alc = 0;
   return 1;
 }