diff --git a/src/aggregate.h b/src/aggregate.h
index 8cd1f5ee34e5..6791dbc2477d 100644
--- a/src/aggregate.h
+++ b/src/aggregate.h
@@ -284,6 +284,7 @@ class ClassDeclaration : public AggregateDeclaration
     bool isFuncHidden(FuncDeclaration *fd);
     FuncDeclaration *findFunc(Identifier *ident, TypeFunction *tf);
     void interfaceSemantic(Scope *sc);
+    unsigned setBaseInterfaceOffsets(unsigned baseOffset);
     bool isCOMclass();
     virtual bool isCOMinterface();
     bool isCPPclass();
diff --git a/src/class.c b/src/class.c
index 366986d2a859..b9e053d2db6a 100644
--- a/src/class.c
+++ b/src/class.c
@@ -995,30 +995,8 @@ void ClassDeclaration::finalizeSize(Scope *sc)
     if (sizeok == SIZEOKfwd)
         return;
 
-    // Allocate instance of each new interface
-    offset = structsize;
-    assert(vtblInterfaces);     // Bugzilla 12984
-    for (size_t i = 0; i < vtblInterfaces->dim; i++)
-    {
-        BaseClass *b = (*vtblInterfaces)[i];
-        unsigned thissize = Target::ptrsize;
-
-        alignmember(STRUCTALIGN_DEFAULT, thissize, &offset);
-        assert(b->offset == 0);
-        b->offset = offset;
-
-        // Take care of single inheritance offsets
-        while (b->baseInterfaces_dim)
-        {
-            b = &b->baseInterfaces[0];
-            b->offset = offset;
-        }
-
-        offset += thissize;
-        if (alignsize < thissize)
-            alignsize = thissize;
-    }
-    structsize = offset;
+    // Add vptr's for any interfaces implemented by this class
+    structsize += setBaseInterfaceOffsets(structsize);
     sizeok = SIZEOKdone;
 
     // Look for the constructor
@@ -1194,6 +1172,39 @@ void ClassDeclaration::interfaceSemantic(Scope *sc)
     }
 }
 
+unsigned ClassDeclaration::setBaseInterfaceOffsets(unsigned baseOffset)
+{
+    assert(vtblInterfaces);     // Bugzilla 12984
+
+    // set the offset of base interfaces from this (most derived) class/interface.
+    unsigned offset = baseOffset;
+
+    //if (vtblInterfaces->dim) printf("\n%s->finalizeSize()\n", toChars());
+    for (size_t i = 0; i < vtblInterfaces->dim; i++)
+    {
+        BaseClass *b = (*vtblInterfaces)[i];
+        unsigned thissize = Target::ptrsize;
+
+        alignmember(STRUCTALIGN_DEFAULT, thissize, &offset);
+        b->offset = offset;
+        //printf("\tvtblInterfaces[%d] b->sym = %s, offset = %d\n", i, b->sym->toChars(), b->offset);
+
+        // Take care of single inheritance offsets
+        while (b->baseInterfaces_dim)
+        {
+            b = &b->baseInterfaces[0];
+            b->offset = offset;
+            //printf("\tvtblInterfaces[%d] +  sym = %s, offset = %d\n", i, b->sym->toChars(), b->offset);
+        }
+
+        offset += thissize;
+        if (alignsize < thissize)
+            alignsize = thissize;
+    }
+
+    return offset - baseOffset;
+}
+
 /****************************************
  */
 
@@ -1613,6 +1624,9 @@ void InterfaceDeclaration::finalizeSize(Scope *sc)
 {
     structsize = Target::ptrsize * 2;
     sizeok = SIZEOKdone;
+
+    // set the offset of base interfaces
+    setBaseInterfaceOffsets(0);
 }
 
 /*******************************************
diff --git a/test/runnable/interface2.d b/test/runnable/interface2.d
index 68f5f42a643b..b4ddae161662 100644
--- a/test/runnable/interface2.d
+++ b/test/runnable/interface2.d
@@ -923,7 +923,7 @@ void test27()
 }
 
 /*******************************************************/
-// 1747
+// 1747 & 2013
 
 void test1747()
 {
@@ -961,11 +961,11 @@ void test1747()
     assert(pia == pc + n);
 
     assert(id.mA() == 1);
-  //assert(id.mB() == 2);   // NG (returns 1, bugzilla 2013 case)
+    assert(id.mB() == 2);   // OK <- NG (bugzilla 2013 case)
     assert(id.mD() == 3);
 
     assert(ic.mA() == 1);
-  //assert(ic.mB() == 2);   // NG (returns 1, bugzilla 2013 case)
+    assert(ic.mB() == 2);   // OK <- NG (bugzilla 2013 case)
 
     assert(ib.mA() == 1);
     assert(ib.mB() == 2);   // OK <- NG