diff --git a/backend/session/direct-freebsd.c b/backend/session/direct-freebsd.c
index cecfb0c1..bce1c871 100644
--- a/backend/session/direct-freebsd.c
+++ b/backend/session/direct-freebsd.c
@@ -1,3 +1,4 @@
+#include <assert.h>
 #include <dev/evdev/input.h>
 #include <errno.h>
 #include <fcntl.h>
@@ -32,8 +33,14 @@ struct direct_session {
 	struct wl_event_source *vt_source;
 };
 
+static struct direct_session *direct_session_from_session(
+		struct wlr_session *base) {
+	assert(base->impl == &session_direct);
+	return (struct direct_session *)base;
+}
+
 static int direct_session_open(struct wlr_session *base, const char *path) {
-	struct direct_session *session = wl_container_of(base, session, base);
+	struct direct_session *session = direct_session_from_session(base);
 
 	int fd = direct_ipc_open(session->sock, path);
 	if (fd < 0) {
@@ -46,7 +53,7 @@ static int direct_session_open(struct wlr_session *base, const char *path) {
 }
 
 static void direct_session_close(struct wlr_session *base, int fd) {
-	struct direct_session *session = wl_container_of(base, session, base);
+	struct direct_session *session = direct_session_from_session(base);
 
 	int ev;
 	struct drm_version dv = {0};
@@ -60,12 +67,12 @@ static void direct_session_close(struct wlr_session *base, int fd) {
 }
 
 static bool direct_change_vt(struct wlr_session *base, unsigned vt) {
-	struct direct_session *session = wl_container_of(base, session, base);
+	struct direct_session *session = direct_session_from_session(base);
 	return ioctl(session->tty_fd, VT_ACTIVATE, (int)vt) == 0;
 }
 
 static void direct_session_destroy(struct wlr_session *base) {
-	struct direct_session *session = wl_container_of(base, session, base);
+	struct direct_session *session = direct_session_from_session(base);
 	struct vt_mode mode = {
 		.mode = VT_AUTO,
 	};
@@ -157,7 +164,8 @@ static bool setup_tty(struct direct_session *session, struct wl_display *display
 	}
 
 	if (ioctl(fd, KDSKBMODE, K_CODE)) {
-		wlr_log_errno(WLR_ERROR, "Failed to set keyboard mode K_CODE on tty %d", tty);
+		wlr_log_errno(WLR_ERROR,
+			"Failed to set keyboard mode K_CODE on tty %d", tty);
 		goto error;
 	}
 
diff --git a/backend/session/direct.c b/backend/session/direct.c
index ed7a0c65..0912cd58 100644
--- a/backend/session/direct.c
+++ b/backend/session/direct.c
@@ -1,4 +1,5 @@
 #define _POSIX_C_SOURCE 200809L
+#include <assert.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <linux/input.h>
@@ -33,8 +34,14 @@ struct direct_session {
 	struct wl_event_source *vt_source;
 };
 
+static struct direct_session *direct_session_from_session(
+		struct wlr_session *base) {
+	assert(base->impl == &session_direct);
+	return (struct direct_session *)base;
+}
+
 static int direct_session_open(struct wlr_session *base, const char *path) {
-	struct direct_session *session = wl_container_of(base, session, base);
+	struct direct_session *session = direct_session_from_session(base);
 
 	int fd = direct_ipc_open(session->sock, path);
 	if (fd < 0) {
@@ -57,7 +64,7 @@ static int direct_session_open(struct wlr_session *base, const char *path) {
 }
 
 static void direct_session_close(struct wlr_session *base, int fd) {
-	struct direct_session *session = wl_container_of(base, session, base);
+	struct direct_session *session = direct_session_from_session(base);
 
 	struct stat st;
 	if (fstat(fd, &st) < 0) {
@@ -76,7 +83,7 @@ static void direct_session_close(struct wlr_session *base, int fd) {
 }
 
 static bool direct_change_vt(struct wlr_session *base, unsigned vt) {
-	struct direct_session *session = wl_container_of(base, session, base);
+	struct direct_session *session = direct_session_from_session(base);
 
 	// Only seat0 has VTs associated with it
 	if (strcmp(session->base.seat, "seat0") != 0) {
@@ -87,7 +94,7 @@ static bool direct_change_vt(struct wlr_session *base, unsigned vt) {
 }
 
 static void direct_session_destroy(struct wlr_session *base) {
-	struct direct_session *session = wl_container_of(base, session, base);
+	struct direct_session *session = direct_session_from_session(base);
 
 	if (strcmp(session->base.seat, "seat0") == 0) {
 		struct vt_mode mode = {
diff --git a/backend/session/logind.c b/backend/session/logind.c
index 2f816b95..39143a2f 100644
--- a/backend/session/logind.c
+++ b/backend/session/logind.c
@@ -37,8 +37,14 @@ struct logind_session {
 	char *path;
 };
 
+static struct logind_session *logind_session_from_session(
+		struct wlr_session *base) {
+	assert(base->impl == &session_logind);
+	return (struct logind_session *)base;
+}
+
 static int logind_take_device(struct wlr_session *base, const char *path) {
-	struct logind_session *session = wl_container_of(base, session, base);
+	struct logind_session *session = logind_session_from_session(base);
 
 	int ret;
 	int fd = -1;
@@ -83,7 +89,7 @@ error:
 }
 
 static void logind_release_device(struct wlr_session *base, int fd) {
-	struct logind_session *session = wl_container_of(base, session, base);
+	struct logind_session *session = logind_session_from_session(base);
 
 	int ret;
 	sd_bus_message *msg = NULL;
@@ -108,7 +114,7 @@ static void logind_release_device(struct wlr_session *base, int fd) {
 }
 
 static bool logind_change_vt(struct wlr_session *base, unsigned vt) {
-	struct logind_session *session = wl_container_of(base, session, base);
+	struct logind_session *session = logind_session_from_session(base);
 
 	// Only seat0 has VTs associated with it
 	if (strcmp(session->base.seat, "seat0") != 0) {
@@ -212,7 +218,7 @@ static void release_control(struct logind_session *session) {
 }
 
 static void logind_session_destroy(struct wlr_session *base) {
-	struct logind_session *session = wl_container_of(base, session, base);
+	struct logind_session *session = logind_session_from_session(base);
 
 	release_control(session);