diff --git a/src/dmd/aggregate.d b/src/dmd/aggregate.d
index f1e6c631675f..622e92324fe8 100644
--- a/src/dmd/aggregate.d
+++ b/src/dmd/aggregate.d
@@ -85,6 +85,10 @@ extern (C++) abstract class AggregateDeclaration : ScopeDsymbol
 
     /// specifies whether this is a D, C++, Objective-C or anonymous struct/class/interface
     ClassKind classKind;
+    /// Specify whether to mangle the aggregate as a `class` or a `struct`
+    /// This information is used by the MSVC mangler
+    /// Only valid for class and struct. TODO: Merge with ClassKind ?
+    CPPMANGLE cppmangle;
 
     /* !=null if is nested
      * pointing to the dsymbol that directly enclosing it.
diff --git a/src/dmd/aggregate.h b/src/dmd/aggregate.h
index fc450a8a214f..717b53f69765 100644
--- a/src/dmd/aggregate.h
+++ b/src/dmd/aggregate.h
@@ -84,6 +84,7 @@ class AggregateDeclaration : public ScopeDsymbol
     Dsymbol *deferred;          // any deferred semantic2() or semantic3() symbol
 
     ClassKind::Type classKind;  // specifies the linkage type
+    CPPMANGLE cppmangle;
 
     /* !=NULL if is nested
      * pointing to the dsymbol that directly enclosing it.
diff --git a/src/dmd/attrib.d b/src/dmd/attrib.d
index a7deb81d2c63..80ceef53283b 100644
--- a/src/dmd/attrib.d
+++ b/src/dmd/attrib.d
@@ -442,6 +442,13 @@ extern (C++) final class CPPMangleDeclaration : AttribDeclaration
             sc.aligndecl, sc.inlining);
     }
 
+    override void setScope(Scope* sc)
+    {
+        if (decl)
+            Dsymbol.setScope(sc); // for forward reference
+        return AttribDeclaration.setScope(sc);
+    }
+
     override const(char)* toChars() const
     {
         return toString().ptr;
diff --git a/src/dmd/attrib.h b/src/dmd/attrib.h
index b0367b4c6953..2795db270b1e 100644
--- a/src/dmd/attrib.h
+++ b/src/dmd/attrib.h
@@ -87,6 +87,7 @@ class CPPMangleDeclaration : public AttribDeclaration
 
     Dsymbol *syntaxCopy(Dsymbol *s);
     Scope *newScope(Scope *sc);
+    void setScope(Scope *sc);
     const char *toChars() const;
     void accept(Visitor *v) { v->visit(this); }
 };
diff --git a/src/dmd/cppmanglewin.d b/src/dmd/cppmanglewin.d
index 863f827aa2e6..918367488264 100644
--- a/src/dmd/cppmanglewin.d
+++ b/src/dmd/cppmanglewin.d
@@ -16,8 +16,10 @@ import core.stdc.stdio;
 
 import dmd.arraytypes;
 import dmd.cppmangle : isPrimaryDtor, isCppOperator, CppOperator;
+import dmd.dclass;
 import dmd.declaration;
 import dmd.denum : isSpecialEnumIdent;
+import dmd.dstruct;
 import dmd.dsymbol;
 import dmd.dtemplate;
 import dmd.errors;
@@ -385,11 +387,12 @@ public:
             return;
         //printf("visit(TypeStruct); is_not_top_type = %d\n", (int)(flags & IS_NOT_TOP_TYPE));
         mangleModifier(type);
-        if (type.sym.isUnionDeclaration())
+        auto agg = cast(StructDeclaration) type.sym;
+        if (agg.isUnionDeclaration())
             buf.writeByte('T');
         else
-            buf.writeByte(type.cppmangle == CPPMANGLE.asClass ? 'V' : 'U');
-        mangleIdent(type.sym);
+            buf.writeByte(agg.cppmangle == CPPMANGLE.asClass ? 'V' : 'U');
+        mangleIdent(agg);
         flags &= ~IS_NOT_TOP_TYPE;
         flags &= ~IGNORE_CONST;
     }
@@ -456,8 +459,9 @@ public:
             buf.writeByte('E');
         flags |= IS_NOT_TOP_TYPE;
         mangleModifier(type);
-        buf.writeByte(type.cppmangle == CPPMANGLE.asStruct ? 'U' : 'V');
-        mangleIdent(type.sym);
+        auto cldecl = cast(ClassDeclaration) type.sym;
+        buf.writeByte(cldecl.cppmangle == CPPMANGLE.asStruct ? 'U' : 'V');
+        mangleIdent(cldecl);
         flags &= ~IS_NOT_TOP_TYPE;
         flags &= ~IGNORE_CONST;
     }
diff --git a/src/dmd/dsymbolsem.d b/src/dmd/dsymbolsem.d
index e25090cb2b44..dd79f34dc047 100644
--- a/src/dmd/dsymbolsem.d
+++ b/src/dmd/dsymbolsem.d
@@ -4639,6 +4639,7 @@ private extern(C++) final class DsymbolSemanticVisitor : Visitor
             if (sc.linkage == LINK.cpp)
                 sd.classKind = ClassKind.cpp;
             sd.cppnamespace = sc.namespace;
+            sd.cppmangle = sc.cppmangle;
         }
         else if (sd.symtab && !scx)
             return;
@@ -4857,6 +4858,7 @@ private extern(C++) final class DsymbolSemanticVisitor : Visitor
             if (sc.linkage == LINK.cpp)
                 cldec.classKind = ClassKind.cpp;
             cldec.cppnamespace = sc.namespace;
+            cldec.cppmangle = sc.cppmangle;
             if (sc.linkage == LINK.objc)
                 objc.setObjc(cldec);
         }
diff --git a/src/dmd/mtype.h b/src/dmd/mtype.h
index a79a62126a1f..c05483dcaf7d 100644
--- a/src/dmd/mtype.h
+++ b/src/dmd/mtype.h
@@ -725,7 +725,6 @@ class TypeStruct : public Type
 public:
     StructDeclaration *sym;
     AliasThisRec att;
-    CPPMANGLE cppmangle;
 
     static TypeStruct *create(StructDeclaration *sym);
     const char *kind();
diff --git a/src/dmd/typesem.d b/src/dmd/typesem.d
index 5baf7ee39cad..4b7238b10445 100644
--- a/src/dmd/typesem.d
+++ b/src/dmd/typesem.d
@@ -1812,14 +1812,7 @@ extern(C++) Type typeSemantic(Type t, Loc loc, Scope* sc)
     {
         //printf("TypeStruct::semantic('%s')\n", mtype.toChars());
         if (mtype.deco)
-        {
-            if (sc && sc.cppmangle != CPPMANGLE.def)
-            {
-                if (mtype.cppmangle == CPPMANGLE.def)
-                    mtype.cppmangle = sc.cppmangle;
-            }
             return mtype;
-        }
 
         /* Don't semantic for sym because it should be deferred until
          * sizeof needed or its members accessed.
@@ -1830,11 +1823,6 @@ extern(C++) Type typeSemantic(Type t, Loc loc, Scope* sc)
         if (mtype.sym.type.ty == Terror)
             return error();
 
-        if (sc && sc.cppmangle != CPPMANGLE.def)
-            mtype.cppmangle = sc.cppmangle;
-        else
-            mtype.cppmangle = CPPMANGLE.asStruct;
-
         return merge(mtype);
     }
 
@@ -1848,14 +1836,7 @@ extern(C++) Type typeSemantic(Type t, Loc loc, Scope* sc)
     {
         //printf("TypeClass::semantic(%s)\n", mtype.toChars());
         if (mtype.deco)
-        {
-            if (sc && sc.cppmangle != CPPMANGLE.def)
-            {
-                if (mtype.cppmangle == CPPMANGLE.def)
-                    mtype.cppmangle = sc.cppmangle;
-            }
             return mtype;
-        }
 
         /* Don't semantic for sym because it should be deferred until
          * sizeof needed or its members accessed.
@@ -1866,11 +1847,6 @@ extern(C++) Type typeSemantic(Type t, Loc loc, Scope* sc)
         if (mtype.sym.type.ty == Terror)
             return error();
 
-        if (sc && sc.cppmangle != CPPMANGLE.def)
-            mtype.cppmangle = sc.cppmangle;
-        else
-            mtype.cppmangle = CPPMANGLE.asClass;
-
         return merge(mtype);
     }
 
diff --git a/test/compilable/cppmangle.d b/test/compilable/cppmangle.d
index 50102e66f74e..739ca5cbad66 100644
--- a/test/compilable/cppmangle.d
+++ b/test/compilable/cppmangle.d
@@ -1251,3 +1251,15 @@ extern(C++, `bar`)
 {
     void func19542(T)();
 }
+
+// https://issues.dlang.org/show_bug.cgi?id=20700
+version (Windows) extern(C++)
+{
+    void test20700_1(Struct20700);
+    extern(C++, class) struct Struct20700 {}
+    void test20700_2(Struct20700);
+
+    // Note: Needs to be `BV` (`class`), not `BU` (`struct`)
+    static assert(test20700_1.mangleof == `?test20700_1@@YAXVStruct20700@@@Z`);
+    static assert(test20700_2.mangleof == `?test20700_2@@YAXVStruct20700@@@Z`);
+}