diff --git a/dlls/oleaut32/tmarshal.c b/dlls/oleaut32/tmarshal.c
index 97500bf944e..9f26a300eeb 100644
--- a/dlls/oleaut32/tmarshal.c
+++ b/dlls/oleaut32/tmarshal.c
@@ -508,9 +508,9 @@ static const IRpcProxyBufferVtbl tmproxyvtable = {
 };
 
 /* how much space do we use on stack in DWORD steps. */
-int
-_argsize(DWORD vt) {
-    switch (vt) {
+static int
+_argsize(TYPEDESC *tdesc, ITypeInfo *tinfo) {
+    switch (tdesc->vt) {
     case VT_UI8:
 	return 8/sizeof(DWORD);
     case VT_R8:
@@ -526,8 +526,9 @@ _argsize(DWORD vt) {
     }
 }
 
+/* how much space do we use on the heap (in bytes) */
 static int
-_xsize(const TYPEDESC *td) {
+_xsize(const TYPEDESC *td, ITypeInfo *tinfo) {
     switch (td->vt) {
     case VT_DATE:
 	return sizeof(DATE);
@@ -539,7 +540,7 @@ _xsize(const TYPEDESC *td) {
 
 	for (i=0;i<adesc->cDims;i++)
 	    arrsize *= adesc->rgbounds[i].cElements;
-	return arrsize*_xsize(&adesc->tdescElem);
+	return arrsize*_xsize(&adesc->tdescElem, tinfo);
     }
     case VT_UI8:
     case VT_I8:
@@ -843,7 +844,7 @@ serialize_param(
 	if (debugout) TRACE_(olerelay)("(vt %s)",debugstr_vt(adesc->tdescElem.vt));
 	if (debugout) TRACE_(olerelay)("[");
 	for (i=0;i<arrsize;i++) {
-	    hres = serialize_param(tinfo, writeit, debugout, dealloc, &adesc->tdescElem, (DWORD*)((LPBYTE)arg+i*_xsize(&adesc->tdescElem)), buf);
+	    hres = serialize_param(tinfo, writeit, debugout, dealloc, &adesc->tdescElem, (DWORD*)((LPBYTE)arg+i*_xsize(&adesc->tdescElem, tinfo)), buf);
 	    if (hres)
 		return hres;
 	    if (debugout && (i<arrsize-1)) TRACE_(olerelay)(",");
@@ -1092,7 +1093,7 @@ deserialize_param(
 	    if (alloc) {
 		/* Allocate space for the referenced struct */
 		if (derefhere)
-		    *arg=(DWORD)HeapAlloc(GetProcessHeap(),HEAP_ZERO_MEMORY,_xsize(tdesc->u.lptdesc));
+		    *arg=(DWORD)HeapAlloc(GetProcessHeap(),HEAP_ZERO_MEMORY,_xsize(tdesc->u.lptdesc, tinfo));
 	    }
 	    if (derefhere)
 		return deserialize_param(tinfo, readit, debugout, alloc, tdesc->u.lptdesc, (LPDWORD)*arg, buf);
@@ -1207,7 +1208,7 @@ deserialize_param(
 		    debugout,
 		    alloc,
 		    &adesc->tdescElem,
-		    (DWORD*)((LPBYTE)(arg)+i*_xsize(&adesc->tdescElem)),
+		    (DWORD*)((LPBYTE)(arg)+i*_xsize(&adesc->tdescElem, tinfo)),
 		    buf
 		);
 	    return S_OK;
@@ -1407,7 +1408,7 @@ xCall(LPVOID retptr, int method, TMProxyImpl *tpinfo /*, args */)
 	}
 	/* No need to marshal other data than FIN and any VT_PTR. */
 	if (!is_in_elem(elem) && (elem->tdesc.vt != VT_PTR)) {
-	    xargs+=_argsize(elem->tdesc.vt);
+	    xargs+=_argsize(&elem->tdesc, tinfo);
 	    if (relaydeb) TRACE_(olerelay)("[out]");
 	    continue;
 	}
@@ -1425,7 +1426,7 @@ xCall(LPVOID retptr, int method, TMProxyImpl *tpinfo /*, args */)
 	    ERR("Failed to serialize param, hres %x\n",hres);
 	    break;
 	}
-	xargs+=_argsize(elem->tdesc.vt);
+	xargs+=_argsize(&elem->tdesc, tinfo);
     }
     if (relaydeb) TRACE_(olerelay)(")");
 
@@ -1466,7 +1467,7 @@ xCall(LPVOID retptr, int method, TMProxyImpl *tpinfo /*, args */)
 	}
 	/* No need to marshal other data than FOUT and any VT_PTR */
 	if (!is_out_elem(elem) && (elem->tdesc.vt != VT_PTR)) {
-	    xargs += _argsize(elem->tdesc.vt);
+	    xargs += _argsize(&elem->tdesc, tinfo);
 	    if (relaydeb) TRACE_(olerelay)("[in]");
 	    continue;
 	}
@@ -1484,7 +1485,7 @@ xCall(LPVOID retptr, int method, TMProxyImpl *tpinfo /*, args */)
 	    status = hres;
 	    break;
 	}
-	xargs += _argsize(elem->tdesc.vt);
+	xargs += _argsize(&elem->tdesc, tinfo);
     }
 
     hres = xbuf_get(&buf, (LPBYTE)&remoteresult, sizeof(DWORD));
@@ -1725,7 +1726,7 @@ static HRESULT init_proxy_entry_point(TMProxyImpl *proxy, unsigned int num)
     /* some args take more than 4 byte on the stack */
     nrofargs = 0;
     for (j=0;j<fdesc->cParams;j++)
-        nrofargs += _argsize(fdesc->lprgelemdescParam[j].tdesc.vt);
+        nrofargs += _argsize(&fdesc->lprgelemdescParam[j].tdesc, proxy->tinfo);
 
 #ifdef __i386__
     if (fdesc->callconv != CC_STDCALL) {
@@ -2055,7 +2056,7 @@ TMStubImpl_Invoke(
     /*dump_FUNCDESC(fdesc);*/
     nrofargs = 0;
     for (i=0;i<fdesc->cParams;i++)
-	nrofargs += _argsize(fdesc->lprgelemdescParam[i].tdesc.vt);
+	nrofargs += _argsize(&fdesc->lprgelemdescParam[i].tdesc, tinfo);
     args = HeapAlloc(GetProcessHeap(),0,(nrofargs+1)*sizeof(DWORD));
     if (!args)
     {
@@ -2077,7 +2078,7 @@ TMStubImpl_Invoke(
 	   xargs,
 	   &buf
 	);
-	xargs += _argsize(elem->tdesc.vt);
+	xargs += _argsize(&elem->tdesc, tinfo);
 	if (hres) {
 	    ERR("Failed to deserialize param %s, hres %x\n",relaystr(names[i+1]),hres);
 	    break;
@@ -2123,7 +2124,7 @@ TMStubImpl_Invoke(
 	   xargs,
 	   &buf
 	);
-	xargs += _argsize(elem->tdesc.vt);
+	xargs += _argsize(&elem->tdesc, tinfo);
 	if (hres) {
 	    ERR("Failed to stuballoc param, hres %x\n",hres);
 	    break;
diff --git a/dlls/oleaut32/typelib.c b/dlls/oleaut32/typelib.c
index 9c7ef98d72c..fb572925be6 100644
--- a/dlls/oleaut32/typelib.c
+++ b/dlls/oleaut32/typelib.c
@@ -5483,7 +5483,32 @@ _invoke(FARPROC func,CALLCONV callconv, int nrargs, DWORD *args) {
     return res;
 }
 
-extern int _argsize(DWORD vt);
+/* The size of the argument on the stack in DWORD units (in all x86 call
+ * convetions the arguments on the stack are DWORD-aligned)
+ */
+int _dispargsize(VARTYPE vt)
+{
+    switch (vt) {
+    case VT_I8:
+    case VT_UI8:
+	return 8/sizeof(DWORD);
+    case VT_R8:
+        return sizeof(double)/sizeof(DWORD);
+    case VT_DECIMAL:
+        return (sizeof(DECIMAL)+3)/sizeof(DWORD);
+    case VT_CY:
+        return sizeof(CY)/sizeof(DWORD);
+    case VT_DATE:
+	return sizeof(DATE)/sizeof(DWORD);
+    case VT_VARIANT:
+	return (sizeof(VARIANT)+3)/sizeof(DWORD);
+    case VT_RECORD:
+        FIXME("VT_RECORD not implemented\n");
+        return 1;
+    default:
+	return 1;
+    }
+}
 
 static HRESULT userdefined_to_variantvt(ITypeInfo *tinfo, const TYPEDESC *tdesc, VARTYPE *vt)
 {
@@ -5671,9 +5696,9 @@ DispCallFunc(
 
     for (i=0;i<cActuals;i++)
     {
-        TRACE("arg %d: type %d, size %d\n",i,prgvt[i],_argsize(prgvt[i]));
+        TRACE("arg %d: type %d, size %d\n",i,prgvt[i],_dispargsize(prgvt[i]));
         dump_Variant(prgpvarg[i]);
-        argsize += _argsize(prgvt[i]);
+        argsize += _dispargsize(prgvt[i]);
     }
     args = HeapAlloc(GetProcessHeap(),0,sizeof(DWORD)*argsize);
 
@@ -5689,10 +5714,10 @@ DispCallFunc(
         VARIANT *arg = prgpvarg[i];
         TRACE("Storing arg %d (%d as %d)\n",i,V_VT(arg),prgvt[i]);
         if (prgvt[i] == VT_VARIANT)
-            memcpy(&args[argspos], arg, _argsize(prgvt[i]) * sizeof(DWORD));
+            memcpy(&args[argspos], arg, _dispargsize(prgvt[i]) * sizeof(DWORD));
         else
-            memcpy(&args[argspos], &V_NONE(arg), _argsize(prgvt[i]) * sizeof(DWORD));
-        argspos += _argsize(prgvt[i]);
+            memcpy(&args[argspos], &V_NONE(arg), _dispargsize(prgvt[i]) * sizeof(DWORD));
+        argspos += _dispargsize(prgvt[i]);
     }
 
     if (pvInstance)