diff --git a/src/backends/av_foundation.rs b/src/backends/av_foundation.rs
index 45a6fbe..68f95c9 100644
--- a/src/backends/av_foundation.rs
+++ b/src/backends/av_foundation.rs
@@ -269,7 +269,7 @@ impl Backend for AvFoundation {
     fn is_speaking(&self) -> Result<bool, Error> {
         trace!("is_speaking()");
         let is_speaking: i8 = unsafe { msg_send![self.synth, isSpeaking] };
-        Ok(is_speaking != NO)
+        Ok(is_speaking != NO as i8)
     }
 }