diff --git a/src/core/emsdevice.cpp b/src/core/emsdevice.cpp
index 9f2ac0dd4..c96561a08 100644
--- a/src/core/emsdevice.cpp
+++ b/src/core/emsdevice.cpp
@@ -2047,7 +2047,7 @@ int EMSdevice::get_modbus_value(uint8_t tag, const std::string & shortname, std:
             return -5;
         }
 
-        for (auto i = 0; i < register_length_s; i++) {
+        for (size_t i = 0; i < register_length_s; i++) {
             auto hi   = (uint8_t)value_s[2 * i];
             auto lo   = (uint8_t)(2 * i + 1 < length_s ? value_s[2 * i + 1] : 0);
             result[i] = ((uint16_t)hi << 8) | lo;
@@ -2165,7 +2165,7 @@ int EMSdevice::modbus_value_to_json(uint8_t tag, const std::string & shortname,
         }
 
         uint32_t value = 0;
-        for (auto i = 0; i < modbus_data.size(); i++) {
+        for (size_t i = 0; i < modbus_data.size(); i++) {
             value += (uint32_t)modbus_data[modbus_data.size() - i - 1] << (i * 8);
         }
 
diff --git a/src/core/emsdevice.h b/src/core/emsdevice.h
index 63cf8b60f..df7e72852 100644
--- a/src/core/emsdevice.h
+++ b/src/core/emsdevice.h
@@ -151,7 +151,7 @@ class EMSdevice {
     }
 
     void has_update(char * value, const char * newvalue, size_t len) {
-        if (value && strcmp(value, newvalue) != 0) {
+        if (value && newvalue && strcmp(value, newvalue) != 0) {
             strlcpy(value, newvalue, len);
             has_update_ = true;
             publish_value(value);