diff --git a/src/tls/tlsv1_cred.c b/src/tls/tlsv1_cred.c
index 3e07245ec..d84648097 100644
--- a/src/tls/tlsv1_cred.c
+++ b/src/tls/tlsv1_cred.c
@@ -244,10 +244,17 @@ static struct crypto_private_key * tlsv1_set_key_pem(const u8 *key, size_t len)
 		if (!end)
 			return NULL;
 	} else {
+		const u8 *pos2;
 		pos += os_strlen(pem_key_begin);
 		end = search_tag(pem_key_end, pos, key + len - pos);
 		if (!end)
 			return NULL;
+		pos2 = search_tag("Proc-Type: 4,ENCRYPTED", pos, end - pos);
+		if (pos2) {
+			wpa_printf(MSG_DEBUG, "TLSv1: Unsupported private key "
+				   "format (Proc-Type/DEK-Info)");
+			return NULL;
+		}
 	}
 
 	der = base64_decode(pos, end - pos, &der_len);