diff --git a/gstreamer/src/caps.rs b/gstreamer/src/caps.rs
index b301c1b3a..0612a3265 100644
--- a/gstreamer/src/caps.rs
+++ b/gstreamer/src/caps.rs
@@ -445,6 +445,8 @@ impl CapsRef {
 
     #[doc(alias = "gst_caps_remove_structure")]
     pub fn remove_structure(&mut self, idx: u32) {
+        assert!(idx < self.size());
+
         unsafe { ffi::gst_caps_remove_structure(self.as_mut_ptr(), idx) }
     }