diff --git a/.build/check-markup-classes.ts b/.build/check-markup-classes.ts
index c21605b4e..934764c16 100644
--- a/.build/check-markup-classes.ts
+++ b/.build/check-markup-classes.ts
@@ -30,7 +30,7 @@ const CLASS_SELECTOR = new RegExp(String.raw`\.(-?(?:${ESCAPE}|[_a-zA-Z\u00a0-\u
 
 const decodeIdent = (ident: string): string => ident.replace(/\\([0-9a-fA-F]{1,6})[ \t\r\n\f]?|\\(.)/g, (_, hex: string | undefined, char: string | undefined) => (hex === undefined ? char! : String.fromCodePoint(parseInt(hex, 16))))
 
-const classNamesIn = (css: string): string[] => [...css.matchAll(CLASS_SELECTOR)].map((m) => decodeIdent(m[1]!))
+const classNamesIn = (css: string): string[] => [...css.matchAll(CLASS_SELECTOR)].map((m) => decodeIdent(m[1]))
 
 const args = process.argv.slice(2)
 const htmlTargets: string[] = []
@@ -84,7 +84,7 @@ const main = async () => {
       pageCount++
       // Page-level <style> blocks define classes too (demo pages style their own markup).
       const inline = new Set<string>()
-      for (const block of html.matchAll(/<style[^>]*>([\s\S]*?)<\/style>/g)) for (const cls of classNamesIn(block[1]!)) inline.add(cls)
+      for (const block of html.matchAll(/<style[^>]*>([\s\S]*?)<\/style>/g)) for (const cls of classNamesIn(block[1])) inline.add(cls)
       for (const m of html.matchAll(/class="([^"]*)"/g)) {
         for (const cls of m[1].split(/\s+/).filter(Boolean)) {
           if (defined.has(cls) || inline.has(cls)) continue
diff --git a/core/js/src/bootstrap/dropdown.ts b/core/js/src/bootstrap/dropdown.ts
index b48e9b8dc..5138f87ce 100644
--- a/core/js/src/bootstrap/dropdown.ts
+++ b/core/js/src/bootstrap/dropdown.ts
@@ -20,7 +20,7 @@ type FloatingConfigFunction = (defaultConfig: FloatingConfig) => Partial<Floatin
 type ComponentConfig = {
   autoClose: boolean | 'inside' | 'outside'
   // A string is Popper's `clippingParents`, kept for v5 markup and mapped to `clippingAncestors`.
-  boundary: Boundary | string
+  boundary: Exclude<Boundary, string> | string
   display: 'dynamic' | 'static'
   offset: number[] | string | ((state: MiddlewareState, element: HTMLElement) => number[])
   popperConfig: Partial<FloatingConfig> | FloatingConfigFunction | null
@@ -210,7 +210,7 @@ class Dropdown extends BaseComponent {
   _getConfig(config?: ComponentConfigInput): ComponentConfig {
     const merged = super._getConfig(config) as ComponentConfig
 
-    if (typeof merged.reference === 'object' && !isElement(merged.reference) && typeof (merged.reference as VirtualElement).getBoundingClientRect !== 'function') {
+    if (typeof merged.reference === 'object' && !isElement(merged.reference) && typeof merged.reference.getBoundingClientRect !== 'function') {
       throw new TypeError(`${NAME.toUpperCase()}: Option "reference" provided type "object" without a required "getBoundingClientRect" method.`)
     }
 
diff --git a/core/js/src/bootstrap/tooltip.ts b/core/js/src/bootstrap/tooltip.ts
index 089d98308..26b84e34c 100644
--- a/core/js/src/bootstrap/tooltip.ts
+++ b/core/js/src/bootstrap/tooltip.ts
@@ -61,7 +61,7 @@ export type TooltipConfig = {
   allowList: AllowList
   animation: boolean
   // A string is Popper's `clippingParents`, kept for v5 markup and mapped to `clippingAncestors`.
-  boundary: Boundary | string
+  boundary: Exclude<Boundary, string> | string
   container: HTMLElement | string | false
   customClass: string | ((this: HTMLElement, element: HTMLElement) => string)
   delay: TooltipDelay
diff --git a/core/js/src/bootstrap/util/floating-ui.ts b/core/js/src/bootstrap/util/floating-ui.ts
index 05b252e68..23e053340 100644
--- a/core/js/src/bootstrap/util/floating-ui.ts
+++ b/core/js/src/bootstrap/util/floating-ui.ts
@@ -118,7 +118,7 @@ class FloatingUi {
     }
 
     if (isElement(reference)) {
-      return getElement(reference as HTMLElement | string)!
+      return getElement(reference)!
     }
 
     if (typeof reference === 'object' && reference !== null) {
@@ -166,12 +166,12 @@ function normalizeOffset(value: unknown): OffsetValue {
   }
 
   if (Array.isArray(raw)) {
-    const [crossAxis = 0, mainAxis = 0] = raw
+    const [crossAxis = 0, mainAxis = 0] = raw as number[]
     return { mainAxis, crossAxis }
   }
 
   if (typeof raw === 'number' || (typeof raw === 'object' && raw !== null)) {
-    return raw as OffsetValue
+    return raw
   }
 
   return 0