diff --git a/rules.mk b/rules.mk
index b140fbca70..f1ca735f2e 100644
--- a/rules.mk
+++ b/rules.mk
@@ -70,6 +70,7 @@ TARGET_SUFFIX=$(call qstrip,$(CONFIG_TARGET_SUFFIX))
 BUILD_SUFFIX:=$(call qstrip,$(CONFIG_BUILD_SUFFIX))
 SUBDIR:=$(patsubst $(TOPDIR)/%,%,${CURDIR})
 BUILD_SUBDIR:=$(patsubst $(TOPDIR)/%,%,${CURDIR})
+NPROC:=$(shell sysctl -n hw.ncpu 2>/dev/null || nproc)
 export SHELL:=/usr/bin/env bash
 
 IS_PACKAGE_BUILD := $(if $(filter package/%,$(BUILD_SUBDIR)),1)
diff --git a/target/imagebuilder/Makefile b/target/imagebuilder/Makefile
index 05c7cf3318..b463feb456 100644
--- a/target/imagebuilder/Makefile
+++ b/target/imagebuilder/Makefile
@@ -86,7 +86,7 @@ endif
 	(cd $(PKG_BUILD_DIR); find staging_dir/host/bin/ $(IB_LDIR)/scripts/dtc/ -type f | \
 		$(XARGS) $(SCRIPT_DIR)/bundle-libraries.sh $(PKG_BUILD_DIR)/staging_dir/host)
 	STRIP=sstrip $(SCRIPT_DIR)/rstrip.sh $(PKG_BUILD_DIR)/staging_dir/host/bin/
-	$(TAR) -cf - -C $(BUILD_DIR) $(IB_NAME) | xz -zc -7e > $@
+	$(TAR) -cf - -C $(BUILD_DIR) $(IB_NAME) | xz -T$(if $(filter 1,$(NPROC)),2,0) -zc -7e > $@
 
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