diff --git a/xcm/src/v3/mod.rs b/xcm/src/v3/mod.rs
index 7aa624b60423..381b65984dbb 100644
--- a/xcm/src/v3/mod.rs
+++ b/xcm/src/v3/mod.rs
@@ -1224,9 +1224,9 @@ impl<Call> TryFrom<OldXcm<Call>> for Xcm<Call> {
 	}
 }
 
-/// Default value for the proof size weight component. Set at 0 KB.
+/// Default value for the proof size weight component when converting from V2. Set at 64 KB.
 /// NOTE: Make sure this is removed after we properly account for PoV weights.
-const DEFAULT_PROOF_SIZE: u64 = 0;
+const DEFAULT_PROOF_SIZE: u64 = 64 * 1024;
 
 // Convert from a v2 instruction to a v3 instruction.
 impl<Call> TryFrom<OldInstruction<Call>> for Instruction<Call> {