diff --git a/lib/env_dpdk/init.c b/lib/env_dpdk/init.c
index 799ba2299..2ea09cc77 100644
--- a/lib/env_dpdk/init.c
+++ b/lib/env_dpdk/init.c
@@ -343,7 +343,7 @@ spdk_build_eal_cmdline(const struct spdk_env_opts *opts)
 
 #if RTE_VERSION >= RTE_VERSION_NUM(18, 05, 0, 0) && RTE_VERSION < RTE_VERSION_NUM(18, 5, 1, 0)
 	/* Dynamic memory management is buggy in DPDK 18.05.0. Don't use it. */
-	if (!opts->env_context || strstr(opts->env_context, "--legacy-mem") != NULL) {
+	if (!opts->env_context || strstr(opts->env_context, "--legacy-mem") == NULL) {
 		args = spdk_push_arg(args, &argcount, _sprintf_alloc("--legacy-mem"));
 		if (args == NULL) {
 			return -1;