diff --git a/bu/CMakeLists.txt b/bu/CMakeLists.txt
index c0d82b3..8c7e486 100644
--- a/bu/CMakeLists.txt
+++ b/bu/CMakeLists.txt
@@ -1,14 +1,20 @@
 cmake_minimum_required(VERSION 3.5)
 project(EPF VERSION 1.0 LANGUAGES CXX)
 
-find_package(Pdal REQUIRED)
+find_package(PDAL REQUIRED)
+if(PDAL_VERSION_MAJOR LESS 2)
+  message(FATAL_ERROR "PDAL version is too old (${PDAL_VERSION}). Use 2.2 or higher.")
+endif()
+if((PDAL_VERSION_MAJOR EQUAL 2) AND (PDAL_VERSION_MINOR LESS 2))
+  message(FATAL_ERROR "PDAL version is too old (${PDAL_VERSION}). Use 2.2 or higher.")
+endif()
 
 file(GLOB SRCS *.cpp)
 
 add_executable(bu ${SRCS})
 
 target_include_directories(bu PRIVATE ${PDAL_INCLUDE_DIRS})
-target_link_libraries(bu PRIVATE ${PDAL_LIBRARIES})
+target_link_libraries(bu PRIVATE ${PDAL_LIBRARIES} pthread)
 
 set_property(TARGET bu PROPERTY CXX_STANDARD 11)
 set_property(TARGET bu PROPERTY CXX_STANDARD_REQUIRED TRUE)
diff --git a/common/GridKey.hpp b/common/GridKey.hpp
index a625cfc..1892deb 100644
--- a/common/GridKey.hpp
+++ b/common/GridKey.hpp
@@ -13,6 +13,10 @@
 
 #pragma once
 
+#include <cassert>
+#include <climits>
+#include <iostream>
+
 namespace ept2
 {
 
diff --git a/epf/CMakeLists.txt b/epf/CMakeLists.txt
index acf8ed4..a876888 100644
--- a/epf/CMakeLists.txt
+++ b/epf/CMakeLists.txt
@@ -1,14 +1,20 @@
 cmake_minimum_required(VERSION 3.5)
 project(EPF VERSION 1.0 LANGUAGES CXX)
 
-find_package(Pdal REQUIRED)
+find_package(PDAL REQUIRED)
+if(PDAL_VERSION_MAJOR LESS 2)
+  message(FATAL_ERROR "PDAL version is too old (${PDAL_VERSION}). Use 2.2 or higher.")
+endif()
+if((PDAL_VERSION_MAJOR EQUAL 2) AND (PDAL_VERSION_MINOR LESS 2))
+  message(FATAL_ERROR "PDAL version is too old (${PDAL_VERSION}). Use 2.2 or higher.")
+endif()
 
 file(GLOB SRCS *.cpp)
 
 add_executable(epf ${SRCS})
 
 target_include_directories(epf PRIVATE ${PDAL_INCLUDE_DIRS})
-target_link_libraries(epf PRIVATE ${PDAL_LIBRARIES})
+target_link_libraries(epf PRIVATE ${PDAL_LIBRARIES} pthread)
 
 set_property(TARGET epf PROPERTY CXX_STANDARD 11)
 set_property(TARGET epf PROPERTY CXX_STANDARD_REQUIRED TRUE)