diff --git a/stew/interval_set.nim b/stew/interval_set.nim
index 538d073..93cd301 100644
--- a/stew/interval_set.nim
+++ b/stew/interval_set.nim
@@ -327,7 +327,7 @@ proc len[P,S](iv: Segm[P,S]): S =
 
 # ------
 
-proc inc[P,S](a: var P; n: S) =
+proc incPt[P,S](a: var P; n: S) =
   ## Might not be generally available for point `P` and scalar `S`
   a = a + n
 
@@ -616,13 +616,13 @@ proc coveredImpl[P,S](ds: IntervalSetRef[P,S]; start: P; length: S): S =
         #    p:         [-------------)
         #    overlap:        <------->
         #
-        result.inc p.right - iv.left
+        result.incPt p.right - iv.left
       else:
         #    iv:             [--------)
         #    p:         [--------------------)
         #    overlap:        <------->
         #
-        result.inc iv.len
+        result.incPt iv.len
       break
     else:
       if iv.right < p.right:
@@ -631,13 +631,13 @@ proc coveredImpl[P,S](ds: IntervalSetRef[P,S]; start: P; length: S): S =
         #    p:              [--------------)
         #    overlap:        <-------->
         #
-        result.inc iv.right - p.left
+        result.incPt iv.right - p.left
       else:
         #    iv:        [----------------------)
         #    p:              [----------)
         #    overlap:        <--------->
         #
-        result.inc p.len
+        result.incPt p.len
 
       iv.size = p.left - iv.left
       #      iv:        [---)
diff --git a/tests/test_sorted_set.nim b/tests/test_sorted_set.nim
index 89ce66b..6df89a2 100644
--- a/tests/test_sorted_set.nim
+++ b/tests/test_sorted_set.nim
@@ -117,25 +117,28 @@ suite "SortedSet: Sorted list based on red-black tree":
   test "Delete items":
     var seen: seq[int]
     let sub7 = keyList.len div 7
-    for n in toSeq(countup(0,sub7)).concat(toSeq(countup(3*sub7,4*sub7))):
-      let
-        key = keyList[n]
-        canDeleteOk = (key notin seen)
+    if sl.len == 0:
+      skip()
+    else:
+      for n in toSeq(countup(0,sub7)).concat(toSeq(countup(3*sub7,4*sub7))):
+        let
+          key = keyList[n]
+          canDeleteOk = (key notin seen)
 
-        data = sl.delete(key)
-        slCheck = sl.verify
+          data = sl.delete(key)
+          slCheck = sl.verify
 
-      if key notin seen:
-        seen.add key
+        if key notin seen:
+          seen.add key
 
-      if slCheck.isErr:
-        check slCheck.error[1] == rbOk # force message
-      check data.isOk == canDeleteOk
+        if slCheck.isErr:
+          check slCheck.error[1] == rbOk # force message
+        check data.isOk == canDeleteOk
 
-      if canDeleteOk:
-        check data.value.key == key
+        if data.isOk: # assuming data.isOk == canDeleteOk if correct
+          check data.value.key == key
 
-    check seen.len + sl.len + rej.len == keyList.len
+      check seen.len + sl.len + rej.len == keyList.len
 
 # ------------------------------------------------------------------------------
 # End