diff --git a/.changeset/smooth-crabs-protect.md b/.changeset/smooth-crabs-protect.md
new file mode 100644
index 0000000000..60bdb1d01e
--- /dev/null
+++ b/.changeset/smooth-crabs-protect.md
@@ -0,0 +1,5 @@
+---
+"@primer/css": patch
+---
+
+This border change was made to ensure that assignee avatars would stack next to one another correctly.
diff --git a/src/avatars/avatar-stack.scss b/src/avatars/avatar-stack.scss
index c7c7b1e209..5b189a3809 100644
--- a/src/avatars/avatar-stack.scss
+++ b/src/avatars/avatar-stack.scss
@@ -56,7 +56,7 @@
     // stylelint-enable selector-max-type
 
     // Account for 4+ avatars
-    &:nth-child(n+4) {
+    &:nth-child(n + 4) {
       display: none;
       opacity: 0;
     }
@@ -68,7 +68,7 @@
       margin-right: 3px;
     }
 
-    .avatar:nth-child(n+4) {
+    .avatar:nth-child(n + 4) {
       display: flex;
       opacity: 1;
     }
@@ -118,6 +118,10 @@
       // stylelint-disable-next-line primer/spacing
       margin-left: 3px;
     }
+
+    .avatar:not(:last-child) {
+      border-left: 0;
+    }
   }
 
   .avatar.avatar-more {