diff --git a/pkgs/development/compilers/swift/compiler/default.nix b/pkgs/development/compilers/swift/compiler/default.nix
index 8e8cf798db4f24..65ce56e00f2f9d 100644
--- a/pkgs/development/compilers/swift/compiler/default.nix
+++ b/pkgs/development/compilers/swift/compiler/default.nix
@@ -64,7 +64,7 @@ let
       #appletvsimulator
       #watchos
       #watchsimulator
-    }.${targetPlatform.darwinPlatform}
+    }."${targetPlatform.darwinPlatform}"
       or (throw "Cannot build Swift for target Darwin platform '${targetPlatform.darwinPlatform}'")
     else targetPlatform.parsed.kernel.name;
 
@@ -583,7 +583,7 @@ in stdenv.mkDerivation {
         #TVOS_SIMULATOR
         #WATCHOS
         #WATCHOS_SIMULATOR
-      }.${targetPlatform.darwinPlatform}}
+      }."${targetPlatform.darwinPlatform}"}
 
       -DLLVM_DIR=$SWIFT_BUILD_ROOT/llvm/lib/cmake/llvm