diff --git a/stdlib/public/core/StringUTF8View.swift b/stdlib/public/core/StringUTF8View.swift
index 41e90fc6f92..f894bbb0ca6 100644
--- a/stdlib/public/core/StringUTF8View.swift
+++ b/stdlib/public/core/StringUTF8View.swift
@@ -330,7 +330,7 @@ extension String.UTF8View {
       let span = unsafe Span(_unsafeStart: start, count: count)
       return unsafe _overrideLifetime(span, borrowing: self)
     }
-#endif
+#endif // _runtime(_ObjC)
     let count = _guts.count
     if _guts.isSmall {
       let a = Builtin.addressOfBorrow(self)
@@ -384,7 +384,7 @@ extension String.UTF8View {
       span
     }
   }
-#else
+#else // !(os(watchOS) && _pointerBitWidth(_32))
   @available(watchOS, unavailable)
   public var span: Span<UTF8.CodeUnit> {
     @lifetime(borrow self)
@@ -415,7 +415,7 @@ extension String.UTF8View {
       return _underlyingSpan()
     }
   }
-#endif
+#endif // !(os(watchOS) && _pointerBitWidth(_32))
 }
 
 // Index conversions
diff --git a/stdlib/public/core/Substring.swift b/stdlib/public/core/Substring.swift
index 60db561adb8..b5b08a28b4b 100644
--- a/stdlib/public/core/Substring.swift
+++ b/stdlib/public/core/Substring.swift
@@ -763,7 +763,7 @@ extension Substring.UTF8View {
       let span = base._underlyingSpan()._extracting(first..<(first &+ count))
       return unsafe _overrideLifetime(span, borrowing: self)
     }
-#endif
+#endif // _runtime(_ObjC)
     let first = _slice._startIndex._encodedOffset
     let end = _slice._endIndex._encodedOffset
     if _wholeGuts.isSmall {
@@ -839,7 +839,7 @@ extension Substring.UTF8View {
       span
     }
   }
-#else
+#else // !(os(watchOS) && _pointerBitWidth(_32))
   @available(watchOS, unavailable)
   public var span: Span<UTF8.CodeUnit> {
     fatalError("\(#function) unavailable on 32-bit watchOS")
@@ -878,7 +878,7 @@ extension Substring.UTF8View {
       return _underlyingSpan()
     }
   }
-#endif
+#endif // !(os(watchOS) && _pointerBitWidth(_32))
 }
 
 extension Substring {
diff --git a/stdlib/public/core/UTF8Span.swift b/stdlib/public/core/UTF8Span.swift
index 6117c273e17..04941a44a4c 100644
--- a/stdlib/public/core/UTF8Span.swift
+++ b/stdlib/public/core/UTF8Span.swift
@@ -213,7 +213,7 @@ extension String {
       let span = unsafe Span(_unsafeStart: start, count: count)
       return unsafe _overrideLifetime(span, borrowing: self)
     }
-#endif
+#endif // _runtime(_ObjC)
     let count = _guts.count
     if _guts.isSmall {
       let a = Builtin.addressOfBorrow(self)
@@ -269,7 +269,7 @@ extension String {
       utf8Span
     }
   }
-#else
+#else // !(os(watchOS) && _pointerBitWidth(_32))
   @available(watchOS, unavailable)
   public var utf8Span: UTF8Span {
     fatalError("\(#function) unavailable on 32-bit watchOS")
@@ -299,7 +299,7 @@ extension String {
       )
     }
   }
-#endif
+#endif // !(os(watchOS) && _pointerBitWidth(_32))
 }
 
 @available(SwiftStdlib 6.2, *)
@@ -316,7 +316,7 @@ extension Substring {
       let span = base._underlyingSpan()._extracting(first..<(first &+ count))
       return unsafe _overrideLifetime(span, borrowing: self)
     }
-#endif
+#endif // _runtime(_ObjC)
     let first = _slice._startIndex._encodedOffset
     let end = _slice._endIndex._encodedOffset
     if _wholeGuts.isSmall {
@@ -394,7 +394,7 @@ extension Substring {
       utf8Span
     }
   }
-#else
+#else // !(os(watchOS) && _pointerBitWidth(_32))
   @available(watchOS, unavailable)
   public var utf8Span: UTF8Span {
     fatalError("\(#function) unavailable on 32-bit watchOS")
@@ -435,5 +435,5 @@ extension Substring {
       )
     }
   }
-#endif
+#endif // !(os(watchOS) && _pointerBitWidth(_32))
 }