diff --git a/.changeset/ripe-symbols-wear.md b/.changeset/ripe-symbols-wear.md
new file mode 100644
index 00000000000..ec8119cbde2
--- /dev/null
+++ b/.changeset/ripe-symbols-wear.md
@@ -0,0 +1,5 @@
+---
+"@spectrum-css/popover": patch
+---
+
+Defines the missing `--spectrum-popover-border-width` custom property. The variable was already being used in our style definitions, but its value was lost at some point so it was undefined in the browser. This work should correct that.
diff --git a/components/popover/dist/metadata.json b/components/popover/dist/metadata.json
index b3a3cd9ac6e..2abca542258 100644
--- a/components/popover/dist/metadata.json
+++ b/components/popover/dist/metadata.json
@@ -144,6 +144,7 @@
     "--spectrum-animation-duration-0",
     "--spectrum-animation-duration-100",
     "--spectrum-background-layer-2-color",
+    "--spectrum-border-width-100",
     "--spectrum-corner-radius-large-default",
     "--spectrum-drop-shadow-elevated-blur",
     "--spectrum-drop-shadow-elevated-color",
diff --git a/components/popover/index.css b/components/popover/index.css
index 48749c9ff61..27722e1eaf6 100644
--- a/components/popover/index.css
+++ b/components/popover/index.css
@@ -18,6 +18,7 @@
 	--spectrum-popover-animation-distance: var(--spectrum-spacing-100);
 
 	--spectrum-popover-background-color: var(--spectrum-background-layer-2-color);
+	--spectrum-popover-border-width: var(--spectrum-border-width-100);
 
 	/* TODO: Cannot use popover-border-color token until the value no longer has the rgba() function alpha/opacity. We should be able to refactor instances of `--spectrum-popover-border-color-rgb` with `--spectrum-popover-border-color` once this is available. */
 	/* --spectrum-popover-border-color-default: var(--spectrum-popover-border-color); */