diff --git a/common/controls.c b/common/controls.c
index 4b4384a8..a52a7584 100644
--- a/common/controls.c
+++ b/common/controls.c
@@ -42,7 +42,7 @@ uint32_t uiControlType(void)
 
 static uint32_t nextControlID = UINT32_C(0x80000000);
 
-uint32_t uiRegisterControlType(const char *name, uiControlVtable *vtable, uiControlOSVtable *osVtable, size_t implDataSize)
+uint32_t uiRegisterControlType(const char *name, const uiControlVtable *vtable, const uiControlOSVtable *osVtable, size_t implDataSize)
 {
 	struct controlType *ct;
 
diff --git a/common/uipriv.h b/common/uipriv.h
index 89888cae..bd84dd22 100644
--- a/common/uipriv.h
+++ b/common/uipriv.h
@@ -70,8 +70,8 @@ uiprivPrintfFunc(
 extern void uiprivReportError(const char *prefix, const char *msg, const char *suffix, bool internal);
 
 // controls.c
-extern bool uiprivOSVtableValid(uiControlOSVtable *osVtable, const char *func);
-extern uiControlOSVtable *uiprivCloneOSVtable(uiControlOSVtable *osVtable);
+extern bool uiprivOSVtableValid(const uiControlOSVtable *osVtable, const char *func);
+extern uiControlOSVtable *uiprivCloneOSVtable(const uiControlOSVtable *osVtable);
 
 #ifdef __cplusplus
 }
diff --git a/darwin/control.m b/darwin/control.m
index 51724e14..0122a26f 100644
--- a/darwin/control.m
+++ b/darwin/control.m
@@ -1,7 +1,7 @@
 // 8 june 2019
 #import "uipriv_darwin.h"
 
-bool uiprivOSVtableValid(uiControlOSVtable *osVtable, const char *func)
+bool uiprivOSVtableValid(const uiControlOSVtable *osVtable, const char *func)
 {
 	if (osVtable->Size != sizeof (uiControlOSVtable)) {
 		uiprivProgrammerErrorWrongStructSize(osVtable->Size, "uiControlOSVtable", func);
@@ -10,7 +10,7 @@ bool uiprivOSVtableValid(uiControlOSVtable *osVtable, const char *func)
 	return true;
 }
 
-uiControlOSVtable *uiprivCloneOSVtable(uiControlOSVtable *osVtable)
+uiControlOSVtable *uiprivCloneOSVtable(const uiControlOSVtable *osVtable)
 {
 	uiControlOSVtable *v2;
 
diff --git a/test/controls.c b/test/controls.c
index b94f07c4..9d359887 100644
--- a/test/controls.c
+++ b/test/controls.c
@@ -17,8 +17,8 @@ static void testVtableFree(uiControl *c, void *implData)
 	// do nothing
 }
 
-const uiControlVtable dummyVtable = {
-	Size:		sizeof (uiControlVtable),
-	Init:		testVtableInit,
-	Free:		testVtableFree,
+const uiControlVtable testVtable = {
+	.Size = sizeof (uiControlVtable),
+	.Init = testVtableInit,
+	.Free = testVtableFree,
 };
diff --git a/test/controls_errors.cpp b/test/controls_errors.cpp
index 4b5930da..41e866f6 100644
--- a/test/controls_errors.cpp
+++ b/test/controls_errors.cpp
@@ -23,7 +23,7 @@ static const struct checkErrorCase cases[] = {
 	
 			memset(&vtable, 0, sizeof (uiControlVtable));
 			vtable.Size = 1;
-			uiRegisterControlSize("name", &vtable, NULL, 0);
+			uiRegisterControlType("name", &vtable, NULL, 0);
 		},
 		"uiRegisterControlType(): wrong size 1 for uiControlVtable",
 	},
diff --git a/ui.h b/ui.h
index 7ba942ba..4a0524b1 100644
--- a/ui.h
+++ b/ui.h
@@ -75,7 +75,7 @@ struct uiControlVtable {
 	void (*Free)(uiControl *c, void *implData);
 };
 
-uiprivExtern uint32_t uiRegisterControlType(const char *nane, uiControlVtable *vtable, uiControlOSVtable *osVtable, size_t implDataSize);
+uiprivExtern uint32_t uiRegisterControlType(const char *nane, const uiControlVtable *vtable, const uiControlOSVtable *osVtable, size_t implDataSize);
 uiprivExtern void *uiCheckControlType(void *c, uint32_t type);
 
 uiprivExtern uiControl *uiNewControl(uint32_t type, void *initData);