diff --git a/src/hotspot/share/gc/shared/genArguments.cpp b/src/hotspot/share/gc/shared/genArguments.cpp
index 76f9f6d40523b..c94ca56722f62 100644
--- a/src/hotspot/share/gc/shared/genArguments.cpp
+++ b/src/hotspot/share/gc/shared/genArguments.cpp
@@ -37,7 +37,11 @@ size_t MinNewSize = 0;
 size_t MinOldSize = 0;
 size_t MaxOldSize = 0;
 
-size_t OldSize = 0;
+// If InitialHeapSize or MinHeapSize is not set on cmdline, this variable,
+// together with NewSize, is used to derive them.
+// Using the same value when it was a configurable flag to avoid breakage.
+// See more in JDK-8346005
+size_t OldSize = ScaleForWordSize(4*M);
 
 size_t GenAlignment = 0;