diff --git a/breakpoint_register.cpp b/breakpoint_register.cpp
index d0f893a..20b2cc2 100644
--- a/breakpoint_register.cpp
+++ b/breakpoint_register.cpp
@@ -79,7 +79,7 @@ std::pair<breakpoint_register *, std::optional<std::string> > breakpoint_registe
 		return { nullptr, "register: key or value missing" };
 
 	auto values_in = parts.at(1);
-	auto v_parts = split(values_in, ",");
+	auto v_parts = split(std::move(values_in), ",");
 	std::set<uint16_t> values;
 	for(auto & v: v_parts)
 		values.insert(std::stoi(v, nullptr, 8));
diff --git a/cpu.cpp b/cpu.cpp
index 68382ab..5fef699 100644
--- a/cpu.cpp
+++ b/cpu.cpp
@@ -346,6 +346,8 @@ bool cpu::check_pending_interrupts() const
 	for(uint8_t i=start_level; i < 8; i++) {
 		auto interrupts = queued_interrupts.find(i);
 
+		assert(interrupts != queued_interrupts.end());
+
 		if (interrupts->second.empty() == false)
 			return true;
 	}
@@ -2316,7 +2318,7 @@ std::map<std::string, std::vector<std::string> > cpu::disassemble(const uint16_t
 	// PSW
 	std::string psw_str = format("%d%d|%d|%d|%c%c%c%c%c", psw >> 14, (psw >> 12) & 3, (psw >> 11) & 1, (psw >> 5) & 7,
                         psw & 16?'t':'-', psw & 8?'n':'-', psw & 4?'z':'-', psw & 2 ? 'v':'-', psw & 1 ? 'c':'-');
-	out.insert({ "psw", { psw_str } });
+	out.insert({ "psw", { std::move(psw_str) } });
 	out.insert({ "psw-value", { format("%06o", psw) } });
 
 	// values worked with
diff --git a/disk_backend_nbd.cpp b/disk_backend_nbd.cpp
index 3067bc7..7e3c7fd 100644
--- a/disk_backend_nbd.cpp
+++ b/disk_backend_nbd.cpp
@@ -119,13 +119,14 @@ bool disk_backend_nbd::connect(const bool retry)
 			}
 		}
 
-		if (memcmp(nbd_hello.magic1, "NBDMAGIC", 8) != 0) {
+		if (fd != -1 && memcmp(nbd_hello.magic1, "NBDMAGIC", 8) != 0) {
 			close(fd);
 			fd = -1;
 			DOLOG(warning, true, "disk_backend_nbd::connect: magic invalid");
 		}
 
-		DOLOG(info, false, "NBD size: %u", NTOHLL(nbd_hello.size));
+		if (fd != -1)
+			DOLOG(info, false, "NBD size: %u", NTOHLL(nbd_hello.size));
 	}
 	while(fd == -1 && retry);