diff --git a/Z80.CPU/v1.0/development/Xcode/Z80.xcodeproj/project.pbxproj b/Z80.CPU/v1.0/development/Xcode/Z80.xcodeproj/project.pbxproj
index f274769..ddb8902 100644
--- a/Z80.CPU/v1.0/development/Xcode/Z80.xcodeproj/project.pbxproj
+++ b/Z80.CPU/v1.0/development/Xcode/Z80.xcodeproj/project.pbxproj
@@ -197,6 +197,7 @@
 				COPY_PHASE_STRIP = NO;
 				GCC_C_LANGUAGE_STANDARD = c99;
 				GCC_DYNAMIC_NO_PIC = NO;
+				GCC_ENABLE_BUILTIN_FUNCTIONS = NO;
 				GCC_GENERATE_DEBUGGING_SYMBOLS = NO;
 				GCC_OPTIMIZATION_LEVEL = 0;
 				GCC_PREPROCESSOR_DEFINITIONS = (
@@ -236,6 +237,7 @@
 				COPY_PHASE_STRIP = YES;
 				DEBUG_INFORMATION_FORMAT = "dwarf-with-dsym";
 				GCC_C_LANGUAGE_STANDARD = c99;
+				GCC_ENABLE_BUILTIN_FUNCTIONS = NO;
 				GCC_GENERATE_DEBUGGING_SYMBOLS = NO;
 				GCC_WARN_64_TO_32_BIT_CONVERSION = YES;
 				GCC_WARN_ABOUT_RETURN_TYPE = YES_ERROR;