diff --git a/libbacktrace/include/backtrace/BacktraceMap.h b/libbacktrace/include/backtrace/BacktraceMap.h
index f8d5058c7..e000a00e2 100644
--- a/libbacktrace/include/backtrace/BacktraceMap.h
+++ b/libbacktrace/include/backtrace/BacktraceMap.h
@@ -79,7 +79,7 @@ public:
       index_++;
       return *this;
     }
-    iterator& operator++(int increment) {
+    const iterator operator++(int increment) {
       index_ += increment;
       return *this;
     }
@@ -87,7 +87,7 @@ public:
       index_--;
       return *this;
     }
-    iterator& operator--(int decrement) {
+    const iterator operator--(int decrement) {
       index_ -= decrement;
       return *this;
     }