diff --git a/src/coreclr/System.Private.CoreLib/src/System/String.CoreCLR.cs b/src/coreclr/System.Private.CoreLib/src/System/String.CoreCLR.cs
index e66db58ba95f52..248b9a91305d80 100644
--- a/src/coreclr/System.Private.CoreLib/src/System/String.CoreCLR.cs
+++ b/src/coreclr/System.Private.CoreLib/src/System/String.CoreCLR.cs
@@ -25,10 +25,10 @@ internal static unsafe string StrCns(uint rid, IntPtr scopeHandle)
         }
 
         [MethodImpl(MethodImplOptions.InternalCall)]
-        internal static extern unsafe string FastAllocateString(MethodTable *pMT, int length);
+        internal static extern unsafe string FastAllocateString(MethodTable *pMT, nint length);
 
         [DebuggerHidden]
-        internal static unsafe string FastAllocateString(int length)
+        internal static unsafe string FastAllocateString(nint length)
         {
             return FastAllocateString(TypeHandle.TypeHandleOf<string>().AsMethodTable(), length);
         }
diff --git a/src/coreclr/interpreter/compiler.cpp b/src/coreclr/interpreter/compiler.cpp
index 2363738a3f725f..c184a263bf1bf5 100644
--- a/src/coreclr/interpreter/compiler.cpp
+++ b/src/coreclr/interpreter/compiler.cpp
@@ -2834,7 +2834,7 @@ void InterpCompiler::EmitCall(CORINFO_RESOLVED_TOKEN* pConstrainedToken, bool re
     if (newObjThisArgLocation != INT_MAX)
     {
         ctorType = GetInterpType(m_compHnd->asCorInfoType(resolvedCallToken.hClass));
-        if (ctorType == InterpTypeVT)
+        if (ctorType != InterpTypeO)
         {
             vtsize = m_compHnd->getClassSize(resolvedCallToken.hClass);
             PushTypeVT(resolvedCallToken.hClass, vtsize);
@@ -2966,7 +2966,7 @@ void InterpCompiler::EmitCall(CORINFO_RESOLVED_TOKEN* pConstrainedToken, bool re
         case CORINFO_CALL:
             if (newObj && !doCallInsteadOfNew)
             {
-                if (ctorType == InterpTypeVT)
+                if (ctorType != InterpTypeO)
                 {
                     // If this is a newobj for a value type, we need to call the constructor
                     // and then copy the value type to the stack.
@@ -5412,6 +5412,18 @@ void InterpCompiler::GenerateCode(CORINFO_METHOD_INFO* methodInfo)
                         m_ip += 5;
                         break;
                     }
+                    case CEE_CPBLK:
+                        CHECK_STACK(3);
+                        if (volatile_)
+                        {
+                            AddIns(INTOP_MEMBAR);
+                            volatile_ = false;
+                        }
+                        AddIns(INTOP_CPBLK);
+                        m_pStackPointer -= 3;
+                        m_pLastNewIns->SetSVars3(m_pStackPointer[0].var, m_pStackPointer[1].var, m_pStackPointer[2].var);
+                        m_ip++;
+                        break;
                     default:
                     {
                         const uint8_t *ip = m_ip - 1;
diff --git a/src/coreclr/interpreter/intops.def b/src/coreclr/interpreter/intops.def
index 0e1d73769a44fa..0861d0f21fbfa7 100644
--- a/src/coreclr/interpreter/intops.def
+++ b/src/coreclr/interpreter/intops.def
@@ -390,6 +390,7 @@ OPDEF(INTOP_GENERICLOOKUP, "generic", 4, 1, 1, InterpOpGenericLookup)
 OPDEF(INTOP_CALL_FINALLY, "call.finally", 2, 0, 0, InterpOpBranch)
 
 OPDEF(INTOP_ZEROBLK_IMM, "zeroblk.imm", 3, 0, 1, InterpOpInt)
+OPDEF(INTOP_CPBLK, "cpblk", 4, 0, 3, InterpOpNoArgs)
 OPDEF(INTOP_LOCALLOC, "localloc", 3, 1, 1, InterpOpNoArgs)
 OPDEF(INTOP_BREAKPOINT, "breakpoint", 1, 0, 0, InterpOpNoArgs)
 
diff --git a/src/coreclr/vm/interpexec.cpp b/src/coreclr/vm/interpexec.cpp
index 2fb4f73e4f2a69..3419a19710d3b3 100644
--- a/src/coreclr/vm/interpexec.cpp
+++ b/src/coreclr/vm/interpexec.cpp
@@ -2012,6 +2012,18 @@ void InterpExecMethod(InterpreterFrame *pInterpreterFrame, InterpMethodContextFr
                     memset(LOCAL_VAR(ip[1], void*), 0, ip[2]);
                     ip += 3;
                     break;
+                case INTOP_CPBLK:
+                {
+                    void* dst = LOCAL_VAR(ip[1], void*);
+                    void* src = LOCAL_VAR(ip[2], void*);
+                    size_t size = LOCAL_VAR(ip[3], size_t);
+                    if (size && (!dst || !src))
+                        COMPlusThrow(kNullReferenceException);
+                    else
+                        memcpyNoGCRefs(dst, src, size);
+                    ip += 4;
+                    break;
+                }
                 case INTOP_LOCALLOC:
                 {
                     size_t len = LOCAL_VAR(ip[2], size_t);