diff --git a/tools/filetop.py b/tools/filetop.py
index ccc5a10..238048e 100755
--- a/tools/filetop.py
+++ b/tools/filetop.py
@@ -119,12 +119,14 @@
 
     struct val_t *valp, zero = {};
     valp = counts.lookup_or_init(&info, &zero);
-    if (is_read) {
-        valp->reads++;
-        valp->rbytes += count;
-    } else {
-        valp->writes++;
-        valp->wbytes += count;
+    if (valp) {
+        if (is_read) {
+            valp->reads++;
+            valp->rbytes += count;
+        } else {
+            valp->writes++;
+            valp->wbytes += count;
+        }
     }
 
     return 0;