Index: sys/kern/kern_environment.c
===================================================================
--- sys/kern/kern_environment.c
+++ sys/kern/kern_environment.c
@@ -359,11 +359,29 @@
 	}
 }
 
+static void
+getfreesuffix(char *cp, size_t *n)
+{
+	size_t len = strlen(cp);
+	char * ncp;
+
+	ncp = malloc(len + 1 + 4 + 1, M_KENV, M_WAITOK);
+	memcpy(ncp, cp, len);
+	for (*n = 1; *n <= 9999; (*n)++) {
+		sprintf(&ncp[len], "_%zu", *n);
+		if (!_getenv_dynamic_locked(ncp, NULL))
+			break;
+	}
+	free(ncp, M_KENV);
+	if (*n > 9999)
+		panic("Too many duplicate kernel environment values: %s", cp);
+}
+
 static void
 init_dynamic_kenv_from(char *init_env, int *curpos)
 {
 	char *cp, *cpnext, *eqpos, *found;
-	size_t len;
+	size_t len, n;
 	int i;
 
 	if (init_env && *init_env != '\0') {
@@ -372,6 +390,12 @@
 		for (cp = init_env; cp != NULL; cp = cpnext) {
 			cpnext = kernenv_next(cp);
 			len = strlen(cp) + 1;
+			if (i > KENV_SIZE) {
+				printf(
+				"WARNING: too many kenv strings, ignoring %s\n",
+				    cp);
+				goto sanitize;
+			}
 			if (len > KENV_MNAMELEN + 1 + kenv_mvallen + 1) {
 				printf(
 				"WARNING: too long kenv string, ignoring %s\n",
@@ -394,18 +418,15 @@
 			 * in the kernel config.
 			 */
 			found = _getenv_dynamic_locked(cp, NULL);
-			*eqpos = '=';
-			if (found != NULL)
-				goto sanitize;
-			if (i > KENV_SIZE) {
-				printf(
-				"WARNING: too many kenv strings, ignoring %s\n",
-				    cp);
-				goto sanitize;
+			if (found != NULL) {
+				getfreesuffix(cp, &n);
+				kenvp[i] = malloc(len + 5, M_KENV, M_WAITOK);
+				sprintf(kenvp[i++], "%s_%zu=%s", cp, n, &eqpos[1]);
+			} else {
+				kenvp[i] = malloc(len, M_KENV, M_WAITOK);
+				*eqpos = '=';
+				strcpy(kenvp[i++], cp);
 			}
-
-			kenvp[i] = malloc(len, M_KENV, M_WAITOK);
-			strcpy(kenvp[i++], cp);
 sanitize:
 #ifdef PRESERVE_EARLY_KENV
 			continue;