diff --git a/buildenv.mk b/buildenv.mk
index 4689c6034..248706dfb 100644
--- a/buildenv.mk
+++ b/buildenv.mk
@@ -285,7 +285,7 @@ endif
 # When `pie' is enabled, the linker (both BFD and Gold) under Ubuntu 14.04
 # will hide all symbols from dynamic symbol table even if they are marked
 # as `global' in the LD version script.
-ENCLAVE_CFLAGS   = -ffreestanding -nostdinc -fvisibility=hidden -fpie -fno-strict-overflow -fno-delete-null-pointer-checks
+ENCLAVE_CFLAGS   = -ffreestanding -nostdinc -fvisibility=hidden -fpie -fno-strict-overflow -fno-delete-null-pointer-checks $(ENCLAVE_SYSTEM_INCLUDES)
 ENCLAVE_CXXFLAGS = $(ENCLAVE_CFLAGS) -nostdinc++
 ENCLAVE_LDFLAGS  = $(ENC_LDFLAGS) $(COMMON_LDFLAGS) -Wl,-Bstatic -Wl,-Bsymbolic -Wl,--no-undefined \
                    -Wl,-pie,-eenclave_entry -Wl,--export-dynamic  \