diff --git a/docs/WASI-api.md b/docs/WASI-api.md
index a89cb963d6..0c721bacd5 100644
--- a/docs/WASI-api.md
+++ b/docs/WASI-api.md
@@ -954,6 +954,9 @@ Inputs:
 
 Write high-quality random data into a buffer.
 
+This function blocks when the implementation is unable to immediately
+provide sufficient high-quality random data.
+
 This function may execute slowly, so when large mounts of random
 data are required, it's advisable to use this function to seed a
 pseudo-random number generator, rather than to provide the