diff --git a/include/swaylock.h b/include/swaylock.h
index 32ded18..56cee3b 100644
--- a/include/swaylock.h
+++ b/include/swaylock.h
@@ -112,7 +112,7 @@ void damage_state(struct swaylock_state *state);
 void clear_password_buffer(struct swaylock_password *pw);
 void schedule_indicator_clear(struct swaylock_state *state);
 
-void initialize_pw_backend(void);
+void initialize_pw_backend(int argc, char **argv);
 void run_pw_backend_child(void);
 void clear_buffer(char *buf, size_t size);
 
diff --git a/main.c b/main.c
index 000b16a..d3921d5 100644
--- a/main.c
+++ b/main.c
@@ -977,7 +977,7 @@ static void comm_in(int fd, short mask, void *data) {
 
 int main(int argc, char **argv) {
 	swaylock_log_init(LOG_ERROR);
-	initialize_pw_backend();
+	initialize_pw_backend(argc, argv);
 
 	enum line_mode line_mode = LM_LINE;
 	state.args = (struct swaylock_args){
diff --git a/pam.c b/pam.c
index 0c21536..a603bd8 100644
--- a/pam.c
+++ b/pam.c
@@ -11,7 +11,13 @@
 
 static char *pw_buf = NULL;
 
-void initialize_pw_backend(void) {
+void initialize_pw_backend(int argc, char **argv) {
+	if (getuid() != geteuid() || getgid() != getegid()) {
+		swaylock_log(LOG_ERROR,
+			"swaylock is setuid, but was compiled with the PAM"
+			" backend. Run 'chmod a-s %s' to fix. Aborting.", argv[0]);
+		exit(EXIT_FAILURE);
+	}
 	if (!spawn_comm_child()) {
 		exit(EXIT_FAILURE);
 	}
diff --git a/shadow.c b/shadow.c
index f98301e..70d00a8 100644
--- a/shadow.c
+++ b/shadow.c
@@ -12,6 +12,32 @@
 #include "log.h"
 #include "swaylock.h"
 
+void initialize_pw_backend(int argc, char **argv) {
+	if (geteuid() != 0) {
+		swaylock_log(LOG_ERROR,
+				"swaylock needs to be setuid to read /etc/shadow");
+		exit(EXIT_FAILURE);
+	}
+
+	if (!spawn_comm_child()) {
+		exit(EXIT_FAILURE);
+	}
+
+	if (setgid(getgid()) != 0) {
+		swaylock_log_errno(LOG_ERROR, "Unable to drop root");
+		exit(EXIT_FAILURE);
+	}
+	if (setuid(getuid()) != 0) {
+		swaylock_log_errno(LOG_ERROR, "Unable to drop root");
+		exit(EXIT_FAILURE);
+	}
+	if (setuid(0) != -1) {
+		swaylock_log_errno(LOG_ERROR, "Unable to drop root (we shouldn't be "
+			"able to restore it after setuid)");
+		exit(EXIT_FAILURE);
+	}
+}
+
 void run_pw_backend_child(void) {
 	/* This code runs as root */
 	struct passwd *pwent = getpwuid(getuid());
@@ -72,30 +98,4 @@ void run_pw_backend_child(void) {
 
 	clear_buffer(encpw, strlen(encpw));
 	exit(EXIT_SUCCESS);
-}
-
-void initialize_pw_backend(void) {
-	if (geteuid() != 0) {
-		swaylock_log(LOG_ERROR,
-				"swaylock needs to be setuid to read /etc/shadow");
-		exit(EXIT_FAILURE);
-	}
-
-	if (!spawn_comm_child()) {
-		exit(EXIT_FAILURE);
-	}
-
-	if (setgid(getgid()) != 0) {
-		swaylock_log_errno(LOG_ERROR, "Unable to drop root");
-		exit(EXIT_FAILURE);
-	}
-	if (setuid(getuid()) != 0) {
-		swaylock_log_errno(LOG_ERROR, "Unable to drop root");
-		exit(EXIT_FAILURE);
-	}
-	if (setuid(0) != -1) {
-		swaylock_log_errno(LOG_ERROR, "Unable to drop root (we shouldn't be "
-			"able to restore it after setuid)");
-		exit(EXIT_FAILURE);
-	}
-}
+}
\ No newline at end of file