diff --git a/src/dials/command_line/simple_tof_integrate.py b/src/dials/command_line/simple_tof_integrate.py
index 4437cb3c18..8c904418c9 100644
--- a/src/dials/command_line/simple_tof_integrate.py
+++ b/src/dials/command_line/simple_tof_integrate.py
@@ -345,6 +345,8 @@ def valid_intensity(intensity, variance):
             )
         )
 
+    if "intensity.prf.value" not in reflections:
+        return
     with open("prf_" + filename, "w") as g:
         for i in range(len(reflections)):
             h, k, l = reflections["miller_index"][i]