diff --git a/extern/libmv/SConscript b/extern/libmv/SConscript
index 60705e913f7..9c134934fa0 100644
--- a/extern/libmv/SConscript
+++ b/extern/libmv/SConscript
@@ -46,16 +46,16 @@ if env['OURPLATFORM'] in ('win32-vc', 'win32-mingw', 'linuxcross', 'win64-vc'):
             defs.append('NDEBUG')
     else:
         if not env['BF_DEBUG']:
-            cflags_libmv = Split(env['REL_CFLAGS'])
-            ccflags_libmv = Split(env['REL_CCFLAGS'])
-            cxxflags_libmv = Split(env['REL_CXXFLAGS'])
+            cflags_libmv += Split(env['REL_CFLAGS'])
+            ccflags_libmv += Split(env['REL_CCFLAGS'])
+            cxxflags_libmv += Split(env['REL_CXXFLAGS'])
 else:
     src += env.Glob("third_party/glog/src/*.cc")
     incs += ' ./third_party/glog/src'
     if not env['BF_DEBUG']:
-        cflags_libmv = Split(env['REL_CFLAGS'])
-        ccflags_libmv = Split(env['REL_CCFLAGS'])
-        cxxflags_libmv = Split(env['REL_CXXFLAGS'])
+        cflags_libmv += Split(env['REL_CFLAGS'])
+        ccflags_libmv += Split(env['REL_CCFLAGS'])
+        cxxflags_libmv += Split(env['REL_CXXFLAGS'])
 
 incs += ' ./third_party/ssba ./third_party/ldl/Include ../colamd/Include'