diff --git a/CMakeLists.txt b/CMakeLists.txt
index 168f4ac..3fb3872 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -174,6 +174,7 @@ endif()
 
 if (NOT EXTERNAL_FMT)
     set(FMT_INCLUDE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/contrib/fmt/include")
+    include_directories(${FMT_INCLUDE_DIR})
 endif()
 
 if (NOT EXTERNAL_CLI11)
@@ -183,7 +184,7 @@ endif()
 include_directories(${CMAKE_CURRENT_SOURCE_DIR}/src ${CMAKE_CURRENT_BINARY_DIR})
 
 find_package(Osmium 2.17.3 REQUIRED COMPONENTS io)
-include_directories(SYSTEM ${OSMIUM_INCLUDE_DIRS} ${PROTOZERO_INCLUDE_DIR} ${FMT_INCLUDE_DIR} ${CLI11_INCLUDE_DIR})
+include_directories(SYSTEM ${OSMIUM_INCLUDE_DIRS} ${PROTOZERO_INCLUDE_DIR} ${CLI11_INCLUDE_DIR})
 
 if (WITH_LUA)
     if (WITH_LUAJIT)