diff --git a/include/utils.h b/include/utils.h
index 8af5a8e973fa..53999c982c56 100644
--- a/include/utils.h
+++ b/include/utils.h
@@ -30,7 +30,7 @@ void __noreturn __abi_breakage(const char *file, int line, const char *reason);
 void __nftnl_assert_fail(uint16_t attr, const char *filename, int line);
 
 #define nftnl_assert(val, attr, expr)			\
-  ((!val || expr)					\
+  ((!val || data_len == 0 || expr)			\
    ? (void)0						\
    : __nftnl_assert_fail(attr, __FILE__, __LINE__))
 
diff --git a/src/chain.c b/src/chain.c
index b4066e4d4e88..94a9e43a1754 100644
--- a/src/chain.c
+++ b/src/chain.c
@@ -364,6 +364,7 @@ const void *nftnl_chain_get_data(const struct nftnl_chain *c, uint16_t attr,
 		*data_len = strlen(c->dev) + 1;
 		return c->dev;
 	case NFTNL_CHAIN_DEVICES:
+		*data_len = 0;
 		return &c->dev_array[0];
 	}
 	return NULL;
diff --git a/src/flowtable.c b/src/flowtable.c
index 1e235d0ba50f..635322d7fa56 100644
--- a/src/flowtable.c
+++ b/src/flowtable.c
@@ -230,6 +230,7 @@ const void *nftnl_flowtable_get_data(const struct nftnl_flowtable *c,
 		*data_len = sizeof(int32_t);
 		return &c->family;
 	case NFTNL_FLOWTABLE_DEVICES:
+		*data_len = 0;
 		return &c->dev_array[0];
 	case NFTNL_FLOWTABLE_SIZE:
 		*data_len = sizeof(int32_t);