diff --git a/lldb/include/lldb/Core/RangeMap.h b/lldb/include/lldb/Core/RangeMap.h
index e917f448df04..c04826164c59 100644
--- a/lldb/include/lldb/Core/RangeMap.h
+++ b/lldb/include/lldb/Core/RangeMap.h
@@ -588,7 +588,13 @@ namespace lldb_private {
         {
             m_entries.clear();
         }
-        
+
+        void
+        Reserve (typename Collection::size_type size)
+        {
+            m_entries.resize (size);
+        }
+
         bool
         IsEmpty () const
         {
@@ -1137,7 +1143,13 @@ namespace lldb_private {
         {
             m_entries.clear();
         }
-        
+
+        void
+        Reserve (typename Collection::size_type size)
+        {
+            m_entries.resize (size);
+        }
+
         bool
         IsEmpty () const
         {
diff --git a/lldb/source/Symbol/DWARFCallFrameInfo.cpp b/lldb/source/Symbol/DWARFCallFrameInfo.cpp
index c8bc08bbd991..d1e7b22f85ed 100644
--- a/lldb/source/Symbol/DWARFCallFrameInfo.cpp
+++ b/lldb/source/Symbol/DWARFCallFrameInfo.cpp
@@ -109,6 +109,8 @@ DWARFCallFrameInfo::GetFunctionAddressAndSizeVector (FunctionAddressAndSizeVecto
 {
     GetFDEIndex();
     const size_t count = m_fde_index.GetSize();
+    function_info.Clear();
+    function_info.Reserve(count);
     for (size_t i = 0; i < count; ++i)
     {
         const FDEEntryMap::Entry *func_offset_data_entry = m_fde_index.GetEntryAtIndex (i);