diff --git a/common/control.c b/common/control.c
index 98cb94aa..8259bdae 100644
--- a/common/control.c
+++ b/common/control.c
@@ -27,7 +27,7 @@ int uiControlToplevel(uiControl *c)
 	return (*(c->Toplevel))(c);
 }
 
-int uiControlVisible(uiControl *c)
+int uiControlVisible(const uiControl *c)
 {
 	return (*(c->Visible))(c);
 }
@@ -42,7 +42,7 @@ void uiControlHide(uiControl *c)
 	(*(c->Hide))(c);
 }
 
-int uiControlEnabled(uiControl *c)
+int uiControlEnabled(const uiControl *c)
 {
 	return (*(c->Enabled))(c);
 }
diff --git a/darwin/window.m b/darwin/window.m
index 1a048207..acc49fbd 100644
--- a/darwin/window.m
+++ b/darwin/window.m
@@ -165,7 +165,7 @@ static int uiWindowToplevel(uiControl *c)
 	return 1;
 }
 
-static int uiWindowVisible(uiControl *c)
+static int uiWindowVisible(const uiControl *c)
 {
 	uiWindow *w = uiWindow(c);
 
diff --git a/ui.h b/ui.h
index 40aea949..a9852456 100644
--- a/ui.h
+++ b/ui.h
@@ -85,10 +85,10 @@ struct uiControl {
 	uiControl *(*Parent)(uiControl *);
 	void (*SetParent)(uiControl *, uiControl *);
 	int (*Toplevel)(uiControl *);
-	int (*Visible)(uiControl *);
+	int (*Visible)(const uiControl *);
 	void (*Show)(uiControl *);
 	void (*Hide)(uiControl *);
-	int (*Enabled)(uiControl *);
+	int (*Enabled)(const uiControl *);
 	void (*Enable)(uiControl *);
 	void (*Disable)(uiControl *);
 };
@@ -99,10 +99,10 @@ _UI_EXTERN uintptr_t uiControlHandle(uiControl *);
 _UI_EXTERN uiControl *uiControlParent(uiControl *);
 _UI_EXTERN void uiControlSetParent(uiControl *, uiControl *);
 _UI_EXTERN int uiControlToplevel(uiControl *);
-_UI_EXTERN int uiControlVisible(uiControl *);
+_UI_EXTERN int uiControlVisible(const uiControl *);
 _UI_EXTERN void uiControlShow(uiControl *);
 _UI_EXTERN void uiControlHide(uiControl *);
-_UI_EXTERN int uiControlEnabled(uiControl *);
+_UI_EXTERN int uiControlEnabled(const uiControl *);
 _UI_EXTERN void uiControlEnable(uiControl *);
 _UI_EXTERN void uiControlDisable(uiControl *);
 
diff --git a/ui_darwin.h b/ui_darwin.h
index c9c6ad54..56fd1d59 100644
--- a/ui_darwin.h
+++ b/ui_darwin.h
@@ -65,7 +65,7 @@ _UI_EXTERN void uiDarwinControlChildVisibilityChanged(uiDarwinControl *);
 		return 0; \
 	}
 #define uiDarwinControlDefaultVisible(type, handlefield) \
-	static int type ## Visible(uiControl *c) \
+	static int type ## Visible(const uiControl *c) \
 	{ \
 		return uiDarwinControl(c)->visible; \
 	}
@@ -84,7 +84,7 @@ _UI_EXTERN void uiDarwinControlChildVisibilityChanged(uiDarwinControl *);
 		uiDarwinNotifyVisibilityChanged(uiDarwinControl(c)); \
 	}
 #define uiDarwinControlDefaultEnabled(type, handlefield) \
-	static int type ## Enabled(uiControl *c) \
+	static int type ## Enabled(const uiControl *c) \
 	{ \
 		return uiDarwinControl(c)->enabled; \
 	}
diff --git a/ui_unix.h b/ui_unix.h
index ed019260..d9056c3a 100644
--- a/ui_unix.h
+++ b/ui_unix.h
@@ -52,7 +52,7 @@ _UI_EXTERN void uiUnixControlSetContainer(uiUnixControl *, GtkContainer *, gbool
 		return 0; \
 	}
 #define uiUnixControlDefaultVisible(type) \
-	static int type ## Visible(uiControl *c) \
+	static int type ## Visible(const uiControl *c) \
 	{ \
 		return gtk_widget_get_visible(type(c)->widget); \
 	}
@@ -69,7 +69,7 @@ _UI_EXTERN void uiUnixControlSetContainer(uiUnixControl *, GtkContainer *, gbool
 		gtk_widget_hide(type(c)->widget); \
 	}
 #define uiUnixControlDefaultEnabled(type) \
-	static int type ## Enabled(uiControl *c) \
+	static int type ## Enabled(const uiControl *c) \
 	{ \
 		return gtk_widget_get_sensitive(type(c)->widget); \
 	}
diff --git a/ui_windows.h b/ui_windows.h
index 69dda366..e21e32ed 100644
--- a/ui_windows.h
+++ b/ui_windows.h
@@ -67,7 +67,7 @@ _UI_EXTERN void uiWindowsControlChildVisibilityChanged(uiWindowsControl *);
 		return 0; \
 	}
 #define uiWindowsControlDefaultVisible(type) \
-	static int type ## Visible(uiControl *c) \
+	static int type ## Visible(const uiControl *c) \
 	{ \
 		return uiWindowsControl(c)->visible; \
 	}
@@ -86,7 +86,7 @@ _UI_EXTERN void uiWindowsControlChildVisibilityChanged(uiWindowsControl *);
 		uiWindowsControlNotifyVisibilityChanged(uiWindowsControl(c)); \
 	}
 #define uiWindowsControlDefaultEnabled(type) \
-	static int type ## Enabled(uiControl *c) \
+	static int type ## Enabled(const uiControl *c) \
 	{ \
 		return uiWindowsControl(c)->enabled; \
 	}
diff --git a/windows/window.cpp b/windows/window.cpp
index 2ea5b7ce..ac8389d3 100644
--- a/windows/window.cpp
+++ b/windows/window.cpp
@@ -194,7 +194,7 @@ static int uiWindowToplevel(uiControl *c)
 }
 
 // TODO initial state of windows is hidden; ensure this here and make it so on other platforms
-static int uiWindowVisible(uiControl *c)
+static int uiWindowVisible(const uiControl *c)
 {
 	uiWindow *w = uiWindow(c);