diff --git a/R/check_dag.R b/R/check_dag.R
index cc5acfea7..dca48df3f 100644
--- a/R/check_dag.R
+++ b/R/check_dag.R
@@ -347,7 +347,7 @@ check_dag <- function(
       # - required is NULL and current adjustment not NULL
       # - OR we have a collider in current adjustments
       incorrectly_adjusted = (is.null(adjustment_set) && !is.null(adjustment_nodes)) ||
-        (!is.null(collider) && collider %in% adjustment_nodes), # nolint
+        (!is.null(collider) && any(collider %in% adjustment_nodes)), # nolint
       current_adjustments = adjustment_nodes,
       minimal_adjustments = minimal_adjustments,
       collider = collider
diff --git a/inst/WORDLIST b/inst/WORDLIST
index d9394796d..847ab8bbe 100644
--- a/inst/WORDLIST
+++ b/inst/WORDLIST
@@ -62,6 +62,7 @@ Dominicy
 Dordrecht
 Dorie
 Dunson
+Dunkler
 Durbin
 Dxy
 Döring
@@ -88,6 +89,8 @@ Gabry
 Gazen
 Gelman
 Gnanadesikan
+Graham
+Gregorich
 Guilford
 Hartig
 HDI
@@ -158,6 +161,7 @@ Michalos
 Moosbrugger
 Monette
 Mora
+Morrissey
 Multicollinearity
 MuMIn
 NFI
@@ -178,6 +182,9 @@ OSF
 OSX
 Olkin
 PNFI
+Papeş
+Pandey
+Park
 Pek
 Petrov
 polychoric
@@ -202,6 +209,7 @@ Rousseeuw
 Routledge
 Rouder
 Rouder's
+Ruxton
 SEM
 SRMR
 Scheepers
@@ -220,6 +228,7 @@ Specifity
 Sphericity
 Springer
 Stata
+Strohmaier
 Subscales
 TLI
 Technometrics
diff --git a/tests/testthat/test-check_dag.R b/tests/testthat/test-check_dag.R
index a25d2ff1f..4414635c2 100644
--- a/tests/testthat/test-check_dag.R
+++ b/tests/testthat/test-check_dag.R
@@ -201,3 +201,21 @@ test_that("check_dag, formula-interface", {
   )
   expect_identical(dag, dag2)
 })
+
+
+test_that("check_dag handles multiple colliders correctly - issue #878", {
+  # This test reproduces the error from issue #878
+  # The DAG has multiple colliders (both 'a' and 'b' are colliders)
+  # because they both have multiple incoming paths from 'c' and 'd'
+  # This test FAILS while bug exists, PASSES after fix
+  expect_no_error(
+    check_dag(
+      y ~ x + a + b,
+      a ~ c + d,
+      b ~ c + d,
+      outcome = "y",
+      exposure = "x",
+      adjusted = ~ a + b
+    )
+  )
+})