diff --git a/platformio.ini b/platformio.ini
index 057ac93..4b308fb 100644
--- a/platformio.ini
+++ b/platformio.ini
@@ -26,6 +26,8 @@ build_unflags =
 build_flags =
   -std=gnu++17
   -O3
+  -Werror
+  -Wall
   -DUSER_SETUP_LOADED=1
   -DLOAD_GLCD=1
   -DLOAD_FONT2=1
diff --git a/src/bmsutils.h b/src/bmsutils.h
index 4d657f6..aa6421f 100644
--- a/src/bmsutils.h
+++ b/src/bmsutils.h
@@ -31,7 +31,7 @@ bool send6Bit(int zhen_tou, int address, int data)
 
     const auto sent = bluetoothSerial.write(buffer, 6);
     if (sent != 6)
-        Serial.printf("send: %lu\r\n", sent);
+        Serial.printf("send: %u\r\n", sent);
     return sent == 6;
 }
 
@@ -53,7 +53,7 @@ void update()
             const auto read = bluetoothSerial.readBytes(buffer, 140);
             if (read != 140)
             {
-                Serial.printf("bms read buffer too short %lu\r\n", read);
+                Serial.printf("bms read buffer too short %u\r\n", read);
 
                 for (int i = 0; i < read; i++)
                     Serial.printf("%i  ", buffer[i]);
diff --git a/src/displays/starfielddisplay.h b/src/displays/starfielddisplay.h
index b996e07..a37c678 100644
--- a/src/displays/starfielddisplay.h
+++ b/src/displays/starfielddisplay.h
@@ -105,7 +105,7 @@ uint8_t StarfieldDisplay::rng()
     zx++;
     za = (za^zc^zx);
     zb = (zb+za);
-    zc = (zc+(zb>>1)^za);
+    zc = (zc+(zb>>1))^za;
     return zc;
 }
 }
diff --git a/src/webserver.h b/src/webserver.h
index f9116c3..ca01466 100644
--- a/src/webserver.h
+++ b/src/webserver.h
@@ -59,13 +59,13 @@ void initWebserver()
 
                 if (auto constCurrentDisplay = static_cast<const Display *>(currentDisplay))
                 {
-                    if (const auto *textInterface = currentDisplay->asTextInterface())
+                    if (const auto *textInterface = constCurrentDisplay->asTextInterface())
                     {
                         HtmlTag h2Tag{"h2", content};
                         content += textInterface->text();
                     }
 
-                    if (const auto *menuDisplay = currentDisplay->asMenuDisplay())
+                    if (const auto *menuDisplay = constCurrentDisplay->asMenuDisplay())
                     {
                         HtmlTag ulTag{"ul", content};
 
@@ -81,7 +81,7 @@ void initWebserver()
                             i++;
                         });
                     }
-                    else if (const auto *changeValueDisplay = currentDisplay->asChangeValueDisplayInterface())
+                    else if (const auto *changeValueDisplay = constCurrentDisplay->asChangeValueDisplayInterface())
                     {
                         content += "<form action=\"/setValue\" method=\"GET\">";
                         content += "<input type=\"number\" name=\"value\" value=\"" + String{changeValueDisplay->shownValue()} + "\" />";
diff --git a/src/widgets/graph.h b/src/widgets/graph.h
index 6c58a91..8c816bc 100644
--- a/src/widgets/graph.h
+++ b/src/widgets/graph.h
@@ -74,7 +74,7 @@ void Graph<LENGTH, COUNT>::redraw(const std::array<std::reference_wrapper<const
 template<size_t LENGTH, size_t COUNT>
 void Graph<LENGTH, COUNT>::render(const std::array<std::reference_wrapper<const ring_buffer<float, LENGTH>>, COUNT> &buffers, bool delta)
 {
-    float min, max;
+    float min{std::numeric_limits<float>::quiet_NaN()}, max{std::numeric_limits<float>::quiet_NaN()};
     bool first{true};
     for (const ring_buffer<float, LENGTH> &buffer : buffers)
     {