diff --git a/ChangeLog b/ChangeLog
index db63a81d0e..6529e08f0f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2012-09-05  Alexandre Oliva  <aoliva@redhat.com>
+
+	* malloc/malloc.c (__libc_mallopt) <M_MMAP_THRESHOLD>: Do not
+	change internal state upon failure.
+
 2012-09-05  Alexandre Oliva  <aoliva@redhat.com>
 
 	* malloc/mcheck.c (mcheck_check_all): Fix typo.
diff --git a/malloc/malloc.c b/malloc/malloc.c
index bd562df959..c69e281389 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -4769,8 +4769,10 @@ int __libc_mallopt(int param_number, int value)
     if((unsigned long)value > HEAP_MAX_SIZE/2)
       res = 0;
     else
-      mp_.mmap_threshold = value;
-      mp_.no_dyn_threshold = 1;
+      {
+	mp_.mmap_threshold = value;
+	mp_.no_dyn_threshold = 1;
+      }
     break;
 
   case M_MMAP_MAX: