diff --git a/library/Makefile b/library/Makefile
index 67f91f6..2f42124 100644
--- a/library/Makefile
+++ b/library/Makefile
@@ -2,6 +2,14 @@
 MBEDTLS_PATH := ..
 endif
 
+ifeq (,$(wildcard $(MBEDTLS_PATH)/framework/exported.make))
+define error_message
+$(MBEDTLS_PATH)/framework/exported.make not found.
+Run `git submodule update --init` to fetch the submodule contents.
+This is a fatal error
+endef
+$(error $(error_message))
+endif
 include $(MBEDTLS_PATH)/framework/exported.make
 
 # Also see "include/mbedtls/mbedtls_config.h"