diff --git a/externals/tz/CMakeLists.txt b/externals/tz/CMakeLists.txt
index c1288e7..3fa28e4 100644
--- a/externals/tz/CMakeLists.txt
+++ b/externals/tz/CMakeLists.txt
@@ -5,7 +5,7 @@ set(TZ_ZONEINFO_DIR "${TZ_DIR}/usr/share/zoneinfo" CACHE PATH "Time zone info da
 set(TZIF_LIST_FILE "${CMAKE_CURRENT_BINARY_DIR}/tzif_list.txt" CACHE PATH "List of zone info files")
 
 find_program(GNU_MAKE make)
-if ("${GNU_MAKE}" STREQUAL "GNU_MAKE-NOTFOUND")
+if (NOT GNU_MAKE)
     message(FATAL_ERROR "GNU make not found")
 endif()
 
diff --git a/src/tzdb/CMakeLists.txt b/src/tzdb/CMakeLists.txt
index 119002b..baf3a88 100644
--- a/src/tzdb/CMakeLists.txt
+++ b/src/tzdb/CMakeLists.txt
@@ -1,10 +1,10 @@
 find_program(GIT_PROGRAM git)
-if ("${GIT_PROGRAM}" STREQUAL "GIT_PROGRAM-NOTFOUND")
+if (NOT GIT_PROGRAM)
     message(FATAL_ERROR "git program not found")
 endif()
 
 find_program(GNU_DATE date)
-if ("${GNU_DATE}" STREQUAL "GNU_DATE-NOTFOUND")
+if (NOT GNU_DATE)
     message(FATAL_ERROR "date program not found")
 endif()