diff --git a/ultragrid/src/audio/playback/coreaudio.c b/ultragrid/src/audio/playback/coreaudio.c
index ffb82b983..aed4d46b0 100644
--- a/ultragrid/src/audio/playback/coreaudio.c
+++ b/ultragrid/src/audio/playback/coreaudio.c
@@ -91,9 +91,10 @@ static OSStatus theRenderProc(void *inRefCon,
         ret = ring_buffer_read(s->buffer, ioData->mBuffers[0].mData, write_bytes);
         ioData->mBuffers[0].mDataByteSize = ret;
 
-        if(!write_bytes) {
+        if(!ret) {
                 fprintf(stderr, "[CoreAudio] Audio buffer underflow.\n");
-                //usleep(10 * 1000 * 1000);
+		memset(ioData->mBuffers[0].mData, 0, write_bytes);
+		ioData->mBuffers[0].mDataByteSize = write_bytes;
         }  
         return noErr;
 }
diff --git a/ultragrid/src/utils/ring_buffer.c b/ultragrid/src/utils/ring_buffer.c
index 8ebb41388..18df161c1 100644
--- a/ultragrid/src/utils/ring_buffer.c
+++ b/ultragrid/src/utils/ring_buffer.c
@@ -113,7 +113,7 @@ void ring_buffer_write(struct ring_buffer * ring, const char *in, int len) {
                 if(read_len_new < 0)
                         read_len_new += ring->len;
                 if(read_len_new < read_len_old) {
-                        fprintf(stderr, "Warning: ring buffer underflow!!!\n");
+                        fprintf(stderr, "Warning: ring buffer overflow!!!\n");
                 }
         }