diff --git a/debian/rules b/debian/rules
index bc784aae..539ac42a 100755
--- a/debian/rules
+++ b/debian/rules
@@ -240,7 +240,7 @@ override_dh_auto_configure: preconfigure
 		-DCMAKE_INSTALL_PREFIX=/usr/lib/llvm-$(LLVM_VERSION) \
 		-DCMAKE_VERBOSE_MAKEFILE=ON \
 		-DCMAKE_BUILD_TYPE=RelWithDebInfo \
-		-DCMAKE_CXX_FLAGS=$(CXXFLAGS_EXTRA) \
+		-DCMAKE_CXX_FLAGS="$(CXXFLAGS_EXTRA)" \
 		-DLLVM_LINK_LLVM_DYLIB=ON \
 		-DLLVM_VERSION_SUFFIX= \
 		-DLLVM_ENABLE_SPHINX=ON \