diff --git a/Transmission.xcodeproj/project.pbxproj b/Transmission.xcodeproj/project.pbxproj
index c42244b04..e7e81fd5f 100644
--- a/Transmission.xcodeproj/project.pbxproj
+++ b/Transmission.xcodeproj/project.pbxproj
@@ -2222,6 +2222,7 @@
 			buildSettings = {
 				COPY_PHASE_STRIP = NO;
 				DEBUG_INFORMATION_FORMAT = dwarf;
+				GCC_C_LANGUAGE_STANDARD = gnu99;
 				GCC_ENABLE_FIX_AND_CONTINUE = YES;
 				GCC_ENABLE_OBJC_EXCEPTIONS = YES;
 				GCC_GENERATE_DEBUGGING_SYMBOLS = YES;
@@ -2354,6 +2355,7 @@
 				);
 				DEBUG_INFORMATION_FORMAT = dwarf;
 				DEPLOYMENT_POSTPROCESSING = YES;
+				GCC_C_LANGUAGE_STANDARD = gnu99;
 				GCC_DEBUGGING_SYMBOLS = used;
 				GCC_ENABLE_OBJC_EXCEPTIONS = YES;
 				GCC_GENERATE_DEBUGGING_SYMBOLS = YES;
@@ -2384,6 +2386,7 @@
 				COPY_PHASE_STRIP = NO;
 				DEBUG_INFORMATION_FORMAT = dwarf;
 				DEPLOYMENT_POSTPROCESSING = YES;
+				GCC_C_LANGUAGE_STANDARD = gnu99;
 				GCC_ENABLE_OBJC_EXCEPTIONS = YES;
 				GCC_GENERATE_DEBUGGING_SYMBOLS = YES;
 				GCC_PRECOMPILE_PREFIX_HEADER = YES;