diff --git a/DESCRIPTION b/DESCRIPTION
index b0fb41c..08c732b 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,7 +1,7 @@
 Package: errorlocate
 Type: Package
 Title: Locate Errors with Validation Rules
-Version: 1.1
+Version: 1.1.1
 Authors@R: c(person("Edwin", "de Jonge", email = "edwindjonge@gmail.com", role = c("aut", "cre"), comment=c(ORCID="0000-0002-6580-4718")),
              person("Mark", "van der Loo", email = "mark.vanderloo@gmail.com", role = c("aut")))
 Description: Errors in data can be located and removed using validation rules from package 
diff --git a/R/categorical.R b/R/categorical.R
index beb3afc..f085f64 100644
--- a/R/categorical.R
+++ b/R/categorical.R
@@ -8,7 +8,7 @@ INFIX_CAT_NAME <- ":"
     return(TRUE)
   }
 
-  if(is.atomic(expr)){
+  if(is.atomic(expr) || is.null(expr)){
     return(is.logical(expr))
   }
 
diff --git a/R/conditional.R b/R/conditional.R
index 371110d..53885a4 100644
--- a/R/conditional.R
+++ b/R/conditional.R
@@ -88,7 +88,7 @@ rep_lin_ <- function(e, or=TRUE, h=new.env()){
   l <- left(e)
   r <- right(e)
 
-  if (is.atomic(e) || is.symbol(e)){
+  if (is.atomic(e) || is.symbol(e) || is.null(e)){
     return(e)
   }
 
diff --git a/R/linear.R b/R/linear.R
index 6c9ecf0..bdec868 100644
--- a/R/linear.R
+++ b/R/linear.R
@@ -48,10 +48,15 @@ is_lin_ <- function(expr, top=TRUE, ...){
     return(is_lin_(l, FALSE) && is_lin_(r, FALSE))
   }
 
+  if (is.null(expr)){
+    return(TRUE)
+  }
+
   if (is.atomic(expr)){
-    return(is.numeric(expr) || is.null(expr))
+    return(is.numeric(expr))
   }
 
+
   if (is.symbol(expr) || op == "var_group"){ return(TRUE) }
 
   if (op %in% c("+","-")){
diff --git a/tests/testthat/test-errorlocation.R b/tests/testthat/test-errorlocation.R
index 029c9f1..ddb1daf 100644
--- a/tests/testthat/test-errorlocation.R
+++ b/tests/testthat/test-errorlocation.R
@@ -31,7 +31,7 @@ describe("errorlocation",{
     rules <- validator( x > 1)
     d <- data.frame( x = c(0,1,2,-1))
     N <- nrow(d)
-    el <- locate_errors(d, rules)
+    el <- locate_errors(d, rules, Ncpus = 1)
 
     expect_equal(length(el$duration), N)
     expect_true(el$duration[3] == 0)