diff --git a/src/ivfkmeans.c b/src/ivfkmeans.c
index 3ae7b2c..d32f071 100644
--- a/src/ivfkmeans.c
+++ b/src/ivfkmeans.c
@@ -282,6 +282,7 @@ MiniBatchKmeans(IvfflatBuildState * buildstate)
 
 	for (i = 0; i < t; i++)
 	{
+		/* Can take a while, so ensure we can interrupt */
 		CHECK_FOR_INTERRUPTS();
 
 		/* Reset samples */