diff --git a/Sources/Xcodeproj/generate().swift b/Sources/Xcodeproj/generate.swift
similarity index 100%
rename from Sources/Xcodeproj/generate().swift
rename to Sources/Xcodeproj/generate.swift
diff --git a/Sources/Xcodeproj/pbxproj().swift b/Sources/Xcodeproj/pbxproj.swift
similarity index 99%
rename from Sources/Xcodeproj/pbxproj().swift
rename to Sources/Xcodeproj/pbxproj.swift
index 36b8d85bc34..e4f84c5f061 100644
--- a/Sources/Xcodeproj/pbxproj().swift
+++ b/Sources/Xcodeproj/pbxproj.swift
@@ -126,6 +126,10 @@ func xcodeProject(
     // paths so that all the products can be found.
     projectSettings.common.DYLIB_INSTALL_NAME_BASE = "@rpath"
 
+    // Set the `Xcode` build preset in Swift to let code conditionalize on
+    // being built in Xcode.
+    projectSettings.common.OTHER_SWIFT_FLAGS = ["$(inherited)", "-DXcode"]
+
     // Add any additional compiler and linker flags the user has specified.
     if !options.flags.cCompilerFlags.isEmpty {
         projectSettings.common.OTHER_CFLAGS = options.flags.cCompilerFlags
@@ -134,12 +138,9 @@ func xcodeProject(
         projectSettings.common.OTHER_LDFLAGS = options.flags.linkerFlags
     }
     if !options.flags.swiftCompilerFlags.isEmpty {
-        projectSettings.common.OTHER_SWIFT_FLAGS = options.flags.swiftCompilerFlags
+        projectSettings.common.OTHER_SWIFT_FLAGS += options.flags.swiftCompilerFlags
     }
 
-    // Also set the `Xcode` build preset in Swift to let code conditionalize on
-    // being built in Xcode.
-    projectSettings.common.OTHER_SWIFT_FLAGS += ["-DXcode"]
     projectSettings.common.MACOSX_DEPLOYMENT_TARGET = "10.10"
 
     // Prevent Xcode project upgrade warnings.