diff --git a/darwin/progressbar.m b/darwin/progressbar.m
index a26874f1..87a9c8d2 100644
--- a/darwin/progressbar.m
+++ b/darwin/progressbar.m
@@ -27,10 +27,31 @@ struct uiProgressBar {
 
 uiDarwinControlAllDefaults(uiProgressBar, pi)
 
+int uiProgressBarValue(uiProgressBar *p)
+{
+	if ([p->pi getIndeterminate]) {
+		return -1;
+	}
+
+	return (int) [p->pi getDoubleValue];
+}
+
 void uiProgressBarSetValue(uiProgressBar *p, int value)
 {
+	if (value == -1) {
+		[p->pi setIndeterminate:YES];
+		[p->pi startAnimation:p->pi];
+		return;
+	}
+
+	if ([p->pi getIndeterminate]) {
+		[p->pi setIndeterminate:NO];
+		[p->pi stopAnimation:p->pi];
+	}
+
 	if (value < 0 || value > 100)
 		userbug("Value %d out of range for a uiProgressBar.", value);
+
 	// on 10.8 there's an animation when the progress bar increases, just like with Aero
 	if (value == 100) {
 		[p->pi setMaxValue:101];
diff --git a/test/page13.c b/test/page13.c
index 0f3f358c..6eb19f29 100644
--- a/test/page13.c
+++ b/test/page13.c
@@ -75,6 +75,20 @@ static void showHide(uiButton *b, void *data)
 		uiControlShow(c);
 }
 
+static void setIndeterminate(uiButton *b, void *data)
+{
+	uiProgressBar *p = uiProgressBar(data);
+
+	int value = uiProgressBarValue(p);
+	if (value == -1) {
+		value = 0;
+	} else {
+		value = -1;
+	}
+
+	uiProgressBarSetValue(p, value);
+}
+
 static void deleteFirst(uiButton *b, void *data)
 {
 	uiForm *f = uiForm(data);
@@ -89,6 +103,7 @@ uiBox *makePage13(void)
 	uiButton *b;
 	uiForm *f;
 	uiEntry *e;
+	uiProgressBar *p;
 
 	page13 = newVerticalBox();
 
@@ -123,6 +138,12 @@ uiBox *makePage13(void)
 
 	uiFormAppend(f, "MLE", uiControl(uiNewMultilineEntry()), 1);
 
+	p = uiNewProgressBar();
+	uiBoxAppend(page13, uiControl(p), 0);
+	b = uiNewButton("Toggle indeterminate");
+	uiButtonOnClicked(b, setIndeterminate, p);
+	uiBoxAppend(page13, uiControl(b), 0);
+
 	b = uiNewButton("Show/Hide");
 	uiButtonOnClicked(b, showHide, e);
 	uiBoxAppend(page13, uiControl(b), 0);
diff --git a/ui.h b/ui.h
index 4fdd9e3e..82079371 100644
--- a/ui.h
+++ b/ui.h
@@ -199,7 +199,7 @@ _UI_EXTERN uiSlider *uiNewSlider(int min, int max);
 
 typedef struct uiProgressBar uiProgressBar;
 #define uiProgressBar(this) ((uiProgressBar *) (this))
-// TODO uiProgressBarValue()
+_UI_EXTERN int uiProgressBarValue(uiProgressBar *p);
 _UI_EXTERN void uiProgressBarSetValue(uiProgressBar *p, int n);
 _UI_EXTERN uiProgressBar *uiNewProgressBar(void);
 
diff --git a/unix/progressbar.c b/unix/progressbar.c
index 40306e6c..9e3fd4a4 100644
--- a/unix/progressbar.c
+++ b/unix/progressbar.c
@@ -5,14 +5,44 @@ struct uiProgressBar {
 	uiUnixControl c;
 	GtkWidget *widget;
 	GtkProgressBar *pbar;
+	int indeterminate;
 };
 
 uiUnixControlAllDefaults(uiProgressBar)
 
+int uiProgressBarValue(uiProgressBar *p)
+{
+	if (p->indeterminate)
+		return -1;
+
+	return (int) (gtk_progress_bar_get_fraction(p->pbar) * 100);
+}
+
+gboolean uiProgressBarPulse(void* data)
+{
+	uiProgressBar *p = (uiProgressBar*) data;
+
+	if (!GTK_IS_WIDGET(p->pbar) || !p->indeterminate)
+		return 0;
+
+	gtk_progress_bar_pulse(p->pbar);
+	return 1;
+}
+
 void uiProgressBarSetValue(uiProgressBar *p, int value)
 {
+	if (value == -1) {
+		if (!p->indeterminate) {
+			p->indeterminate = 1;
+			g_timeout_add(100, uiProgressBarPulse, p);
+		}
+		return;
+	}
+
 	if (value < 0 || value > 100)
 		userbug("Value %d is out of range for a uiProgressBar.", value);
+
+	p->indeterminate = 0;
 	gtk_progress_bar_set_fraction(p->pbar, ((gdouble) value) / 100);
 }
 
diff --git a/windows/progressbar.cpp b/windows/progressbar.cpp
index d16569ad..2d155de1 100644
--- a/windows/progressbar.cpp
+++ b/windows/progressbar.cpp
@@ -26,14 +26,40 @@ static void uiProgressBarMinimumSize(uiWindowsControl *c, int *width, int *heigh
 	*height = y;
 }
 
+int uiProgressBarValue(uiProgressBar *p)
+{
+	LONG_PTR style = GetWindowLongPtr(p->hwnd, GWL_STYLE);
+	if ((style & PBS_MARQUEE) != 0) {
+		return -1;
+	}
+
+	return (int) SendMessage(p->hwnd, PBM_GETPOS, 0, 0);
+}
+
 // unfortunately, as of Vista progress bars have a forced animation on increase
 // we have to set the progress bar to value + 1 and decrease it back to value if we want an "instant" change
 // see http://stackoverflow.com/questions/2217688/windows-7-aero-theme-progress-bar-bug
 // it's not ideal/perfect, but it will have to do
 void uiProgressBarSetValue(uiProgressBar *p, int value)
 {
+	LONG_PTR style = GetWindowLongPtr(p->hwnd, GWL_STYLE);
+
+	if (value == -1) {
+		if ((style & PBS_MARQUEE) == 0) {
+			SetWindowLongPtr(p->hwnd, GWL_STYLE, style | PBS_MARQUEE);
+			SendMessage(p->hwnd, PBM_SETMARQUEE, 1, 0);
+		}
+		return;
+	}
+
+	if ((style & PBS_MARQUEE) != 0) {
+		SetWindowLongPtr(p->hwnd, GWL_STYLE, style ^ PBS_MARQUEE);
+		SendMessage(p->hwnd, PBM_SETMARQUEE, 0, 0);
+	}
+
 	if (value < 0 || value > 100)
 		userbug("Value %d is out of range for uiProgressBars.", value);
+
 	if (value == 100) {			// because we can't 101
 		SendMessageW(p->hwnd, PBM_SETRANGE32, 0, 101);
 		SendMessageW(p->hwnd, PBM_SETPOS, 101, 0);