diff --git a/sdk/bpf/bpf.mk b/sdk/bpf/bpf.mk
index 1a9971cbb2..a728158c1d 100644
--- a/sdk/bpf/bpf.mk
+++ b/sdk/bpf/bpf.mk
@@ -12,7 +12,7 @@ INC_DIRS ?=
 SRC_DIR ?= ./src
 TEST_DIR ?= ./test
 OUT_DIR ?= ./out
-OS := $(uname)
+OS := $(shell uname)
 
 ifeq ($(DOCKER),1)
 LLVM_DIR = $(LOCAL_PATH)llvm-docker/