diff --git a/ff/CMakeLists.txt b/ff/CMakeLists.txt
index f4a1194..857a8fd 100644
--- a/ff/CMakeLists.txt
+++ b/ff/CMakeLists.txt
@@ -35,6 +35,11 @@ set(CMAKE_C_EXTENSIONS ON)
 set(CMAKE_C_STANDARD_REQUIRED ON)
 set(CMAKE_C_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wextra -Werror \
     -Wshadow -Wunused-parameter -Wformat -Wpointer-arith -Wundef")
+include(CheckCCompilerFlag)
+check_c_compiler_flag(-fzero-init-padding-bits HAS_ZERO_INIT_PADDING_BITS)
+if (HAS_ZERO_INIT_PADDING_BITS)
+    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fzero-init-padding-bits=unions")
+endif()
 set(CMAKE_C_FLAGS_RELEASE "-O3")
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 if(NOT CMAKE_BUILD_TYPE)
diff --git a/ubloxcfg/CMakeLists.txt b/ubloxcfg/CMakeLists.txt
index 74b5c83..4ac77d7 100644
--- a/ubloxcfg/CMakeLists.txt
+++ b/ubloxcfg/CMakeLists.txt
@@ -35,6 +35,11 @@ set(CMAKE_C_EXTENSIONS OFF)
 set(CMAKE_C_STANDARD_REQUIRED ON)
 set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall -Wextra -Wpedantic -Werror \
     -Wshadow -Wunused-parameter -Wformat -Wpointer-arith -Wundef")
+include(CheckCCompilerFlag)
+check_c_compiler_flag(-fzero-init-padding-bits HAS_ZERO_INIT_PADDING_BITS)
+if (HAS_ZERO_INIT_PADDING_BITS)
+    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fzero-init-padding-bits=unions")
+endif()
 set(CMAKE_C_FLAGS_RELEASE "-O3")
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 if(NOT CMAKE_BUILD_TYPE)