diff --git a/arm-toolchain.cmake b/arm-toolchain.cmake
index f15b72bac2..1425b2b450 100644
--- a/arm-toolchain.cmake
+++ b/arm-toolchain.cmake
@@ -4,6 +4,6 @@ set(ARM_PREFIX arm-frc-linux-gnueabi)
 set(CMAKE_SYSTEM_NAME Linux)
 CMAKE_FORCE_CXX_COMPILER(${ARM_PREFIX}-g++ GNU)
 CMAKE_FORCE_C_COMPILER(${ARM_PREFIX}-gcc GNU)
-set(CMAKE_CXX_FLAGS "-std=c++1y -Wformat=2 -Wall -Wextra -Wno-psabi" CACHE STRING "" FORCE)
+set(CMAKE_CXX_FLAGS "-std=c++1y -Wformat=2 -Wall -Wextra -Werror -Wno-psabi" CACHE STRING "" FORCE)
 set(CMAKE_CXX_FLAGS_DEBUG "-O0 -g3" CACHE STRING "" FORCE)
 set(CMAKE_CXX_FLAGS_RELEASE "-O3 -g" CACHE STRING "" FORCE) # still want debugging for release?
diff --git a/hal/lib/Athena/ctre/CtreCanNode.h b/hal/lib/Athena/ctre/CtreCanNode.h
index ead88b43e0..263fcdb2fd 100644
--- a/hal/lib/Athena/ctre/CtreCanNode.h
+++ b/hal/lib/Athena/ctre/CtreCanNode.h
@@ -90,7 +90,7 @@ private:
 			uint32_t periodMs;
 			txJob_t() : arbId(0),periodMs(0)
 			{
-				for(int i=0;i<sizeof(toSend);++i)
+				for(unsigned i=0;i<sizeof(toSend);++i)
 					toSend[i] = 0;
 			}
 	};
diff --git a/wpilibc/wpilibC++Devices/src/CANJaguar.cpp b/wpilibc/wpilibC++Devices/src/CANJaguar.cpp
index 62226c89c8..8631e7e9d4 100644
--- a/wpilibc/wpilibC++Devices/src/CANJaguar.cpp
+++ b/wpilibc/wpilibC++Devices/src/CANJaguar.cpp
@@ -1837,10 +1837,9 @@ void CANJaguar::ConfigNeutralMode(NeutralMode mode)
 void CANJaguar::ConfigEncoderCodesPerRev(uint16_t codesPerRev)
 {
 	uint8_t dataBuffer[8];
-	uint8_t dataSize;
 
 	// Set the codes per revolution mode
-	dataSize = packint16_t(dataBuffer, codesPerRev);
+	packint16_t(dataBuffer, codesPerRev);
 	sendMessage(LM_API_CFG_ENC_LINES, dataBuffer, sizeof(uint16_t));
 
 	m_encoderCodesPerRev = codesPerRev;