diff --git a/lib/CMakeLists.txt b/lib/CMakeLists.txt
index a29e9770d9115..e76023e5c3311 100644
--- a/lib/CMakeLists.txt
+++ b/lib/CMakeLists.txt
@@ -40,10 +40,10 @@ if (SWIFT_SWIFT_PARSER)
 
   # Determine the SwiftSyntax shared library files that were built as
   # part of earlyswiftsyntax.
-  list(TRANSFORM SWIFT_SYNTAX_MODULES PREPEND ${CMAKE_SHARED_LIBRARY_PREFIX}
+  list(TRANSFORM SWIFT_SYNTAX_MODULES PREPEND "${CMAKE_SHARED_LIBRARY_PREFIX}"
        OUTPUT_VARIABLE SWIFT_SYNTAX_SHARED_LIBRARIES)
   list(TRANSFORM SWIFT_SYNTAX_SHARED_LIBRARIES APPEND
-       ${CMAKE_SHARED_LIBRARY_SUFFIX}
+       "${CMAKE_SHARED_LIBRARY_SUFFIX}"
        OUTPUT_VARIABLE SWIFT_SYNTAX_SHARED_LIBRARIES)
 
   # Interface library to collect swiftinterfaces and swiftmodules from