diff --git a/CMakeLists.txt b/CMakeLists.txt
index bdaefb0d590..4724e101603 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1156,6 +1156,12 @@ if(UNIX AND NOT APPLE)
 	# GNU Compiler
 	if(CMAKE_COMPILER_IS_GNUCC)
 		set(PLATFORM_CFLAGS "-pipe -fPIC -funsigned-char -fno-strict-aliasing")
+
+		if(NOT "${CMAKE_C_COMPILER_VERSION}" VERSION_LESS "5.0")
+			# GCC5 uses gnu11, until we update, force c89
+			# though some c11 features can still be used.
+			set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -std=gnu89")
+		endif()
 	# CLang is the same as GCC for now.
 	elseif(CMAKE_C_COMPILER_ID MATCHES "Clang")
 		set(PLATFORM_CFLAGS "-pipe -fPIC -funsigned-char -fno-strict-aliasing")
diff --git a/build_files/scons/config/linux-config.py b/build_files/scons/config/linux-config.py
index 455dd23cdb3..c3f0c434081 100644
--- a/build_files/scons/config/linux-config.py
+++ b/build_files/scons/config/linux-config.py
@@ -230,7 +230,7 @@ WITH_BF_FREESTYLE = True
 CC = 'gcc'
 CXX = 'g++'
 
-CCFLAGS = ['-pipe','-fPIC','-funsigned-char','-fno-strict-aliasing','-D_LARGEFILE_SOURCE', '-D_FILE_OFFSET_BITS=64','-D_LARGEFILE64_SOURCE']
+CCFLAGS = ['-pipe','-fPIC','-funsigned-char','-fno-strict-aliasing', '-std=gnu89', '-D_LARGEFILE_SOURCE', '-D_FILE_OFFSET_BITS=64','-D_LARGEFILE64_SOURCE']
 CXXFLAGS = []
 
 CPPFLAGS = []