diff --git a/ext/googletest/SConscript b/ext/googletest/SConscript
index 6792a75..e5241d6 100644
--- a/ext/googletest/SConscript
+++ b/ext/googletest/SConscript
@@ -43,14 +43,16 @@
 main.Append(CPPPATH=[gtest_include, gmock_include])
 main.Append(LIBPATH=[build])
 
-env = main.Clone(CPPFLAGS='-g -Wall -Wextra -pthread'
-                          ' -Wno-undef -isystem %s -isystem %s' % (gtest_include, gmock_include))
+env = main.Clone(CPPFLAGS=['-g', '-Wall', '-Wextra', '-pthread',
+                           '-Wno-undef', '-isystem', str(gtest_include),
+                           '-isystem', str(gmock_include)])
 env.Append(CPPPATH=[gtest_base, gmock_base])
 
 gtest_all = env.Object(gtest_src.File('gtest-all.cc'))
 gmock_all = env.Object(gmock_src.File('gmock-all.cc'))
-gtest_main = env.StaticLibrary(
-    target='libgtest', source=[gtest_all, gmock_all, gtest_src.File('gtest_main.cc')])
+gtest_main = env.StaticLibrary(target='libgtest', source=[
+        gtest_all, gmock_all, gtest_src.File('gtest_main.cc')])
 
 main['GTEST_LIBS'] = ['libgtest', 'pthread']
-main['GTEST_CPPFLAGS'] = '-pthread -DUSE_GMOCK -Wno-undef -isystem %s' % gtest_include.abspath
+main['GTEST_CPPFLAGS'] = [
+    '-pthread', '-DUSE_GMOCK', '-Wno-undef', '-isystem', gtest_include.abspath]