diff --git a/DESCRIPTION b/DESCRIPTION
index 45c7a283..6446df71 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,7 +1,7 @@
 Type: Package
 Package: effectsize
 Title: Indices of Effect Size
-Version: 0.8.6.5
+Version: 0.8.6.6
 Authors@R: 
     c(person(given = "Mattan S.",
              family = "Ben-Shachar",
diff --git a/NEWS.md b/NEWS.md
index 4fa67482..8fe69bac 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -11,6 +11,7 @@
   
 ## Bug fixes
 
+- Minor stability fix to ncp-based CI methods ( #628 )
 - `nnt()` now properly accepts the `y` argument.
 
 # effectsize 0.8.7
diff --git a/R/docs_extra.R b/R/docs_extra.R
index 39249d9f..cb133e6b 100644
--- a/R/docs_extra.R
+++ b/R/docs_extra.R
@@ -124,13 +124,8 @@
 #' smaller than the tolerance of the optimizer, resulting in CIs of width 0.
 #' This can also result in the estimated CIs excluding the point estimate.
 #'
-#' For example:
-#' ```{r}
-#' t_to_d(80, df_error = 4555555)
-#' ```
-#'
-#' In these cases, consider an alternative optimizer, or an alternative method
-#' for computing CIs, such as the bootstrap.
+#' In these cases, consider an alternative method for computing CIs, such as the
+#' bootstrap.
 #'
 #'
 #' @references
diff --git a/R/utils_ci.R b/R/utils_ci.R
index 20950705..9f36db72 100644
--- a/R/utils_ci.R
+++ b/R/utils_ci.R
@@ -15,10 +15,8 @@
   ncp <- suppressWarnings(stats::optim(
     par = 1.1 * rep(lambda, 2),
     fn = function(x) {
-      p <- stats::pf(q = f, df, df_error, ncp = x)
-
-      abs(max(p) - probs[2]) +
-        abs(min(p) - probs[1])
+      q <- stats::qf(p = probs, df, df_error, ncp = x)
+      sum(abs(q - f))
     },
     control = list(abstol = 1e-09)
   ))
@@ -37,10 +35,9 @@
 
 #' @keywords internal
 .get_ncp_t <- function(t, df_error, conf.level = 0.95) {
-  # # Note: these aren't actually needed - all t related functions would fail earlier
-  # if (!is.finite(t) || !is.finite(df_error)) {
-  #   return(c(NA, NA))
-  # }
+  if (!is.finite(t) || !is.finite(df_error)) {
+    return(c(NA, NA))
+  }
 
   alpha <- 1 - conf.level
   probs <- c(alpha / 2, 1 - alpha / 2)
@@ -48,45 +45,41 @@
   ncp <- suppressWarnings(stats::optim(
     par = 1.1 * rep(t, 2),
     fn = function(x) {
-      p <- stats::pt(q = t, df = df_error, ncp = x)
-
-      abs(max(p) - probs[2]) +
-        abs(min(p) - probs[1])
+      q <- stats::qt(p = probs, df = df_error, ncp = x)
+      sum(abs(q - t))
     },
     control = list(abstol = 1e-09)
   ))
+
   t_ncp <- unname(sort(ncp$par))
 
   return(t_ncp)
 }
 
 #' @keywords internals
-.get_ncp_chi <- function(chi, df, conf.level = 0.95) {
-  # # Note: these aren't actually needed - all chisq related functions would fail earlier
-  # if (!is.finite(chi) || !is.finite(df)) {
-  #   return(c(NA, NA))
-  # }
+.get_ncp_chi <- function(chisq, df, conf.level = 0.95) {
+  if (!is.finite(chisq) || !is.finite(df)) {
+    return(c(NA, NA))
+  }
 
   alpha <- 1 - conf.level
   probs <- c(alpha / 2, 1 - alpha / 2)
 
   ncp <- suppressWarnings(stats::optim(
-    par = 1.1 * rep(chi, 2),
+    par = 1.1 * rep(chisq, 2),
     fn = function(x) {
-      p <- stats::pchisq(q = chi, df, ncp = x)
-
-      abs(max(p) - probs[2]) +
-        abs(min(p) - probs[1])
+      q <- stats::qchisq(p = probs, df, ncp = x)
+      sum(abs(q - chisq))
     },
     control = list(abstol = 1e-09)
   ))
   chi_ncp <- sort(ncp$par)
 
-  if (chi <= stats::qchisq(probs[1], df)) {
+  if (chisq <= stats::qchisq(probs[1], df)) {
     chi_ncp[2] <- 0
   }
 
-  if (chi <= stats::qchisq(probs[2], df)) {
+  if (chisq <= stats::qchisq(probs[2], df)) {
     chi_ncp[1] <- 0
   }
 
diff --git a/man/cohens_d.Rd b/man/cohens_d.Rd
index 60236654..6a67d0b3 100644
--- a/man/cohens_d.Rd
+++ b/man/cohens_d.Rd
@@ -38,7 +38,7 @@ glass_delta(
   y = NULL,
   data = NULL,
   mu = 0,
-  adjust = FALSE,
+  adjust = TRUE,
   ci = 0.95,
   alternative = "two.sided",
   verbose = TRUE,
diff --git a/man/effectsize-package.Rd b/man/effectsize-package.Rd
index 30c9a441..6cd2eb23 100644
--- a/man/effectsize-package.Rd
+++ b/man/effectsize-package.Rd
@@ -47,6 +47,7 @@ Authors:
   \item Indrajeet Patil \email{patilindrajeet.science@gmail.com} (\href{https://orcid.org/0000-0003-1995-6531}{ORCID}) (@patilindrajeets)
   \item Brenton M. Wiernik \email{brenton@wiernik.org} (\href{https://orcid.org/0000-0001-9560-6336}{ORCID}) (@bmwiernik)
   \item Rémi Thériault \email{remi.theriault@mail.mcgill.ca} (\href{https://orcid.org/0000-0003-4315-6788}{ORCID}) (@rempsyc)
+  \item Philip Waggoner \email{philip.waggoner@gmail.com} (\href{https://orcid.org/0000-0002-7825-7573}{ORCID}) [contributor]
 }
 
 Other contributors:
diff --git a/man/effectsize_CIs.Rd b/man/effectsize_CIs.Rd
index 8f848c60..db30b81c 100644
--- a/man/effectsize_CIs.Rd
+++ b/man/effectsize_CIs.Rd
@@ -155,16 +155,8 @@ For very large sample sizes or effect sizes, the width of the CI can be
 smaller than the tolerance of the optimizer, resulting in CIs of width 0.
 This can also result in the estimated CIs excluding the point estimate.
 
-For example:
-
-\if{html}{\out{<div class="sourceCode r">}}\preformatted{t_to_d(80, df_error = 4555555)
-#> d    |       95\% CI
-#> -------------------
-#> 0.07 | [0.08, 0.08]
-}\if{html}{\out{</div>}}
-
-In these cases, consider an alternative optimizer, or an alternative method
-for computing CIs, such as the bootstrap.
+In these cases, consider an alternative method for computing CIs, such as the
+bootstrap.
 }
 
 \references{