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];