diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index a85e025c3..0e6e3cde1 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -1,9 +1,38 @@
+################################################################################
+# API header files
+################################################################################
+# This lists the API header files that are scanned by
+# some of the build rules to generate some files needed
+# by the build
+set(Z3_API_HEADER_FILES_TO_SCAN
+  z3_api.h
+  z3_ast_containers.h
+  z3_algebraic.h
+  z3_polynomial.h
+  z3_rcf.h
+  z3_fixedpoint.h
+  z3_optimization.h
+  z3_interp.h
+  z3_fpa.h
+)
+set(Z3_FULL_PATH_API_HEADER_FILES_TO_SCAN "")
+foreach (header_file ${Z3_API_HEADER_FILES_TO_SCAN})
+  set(full_path_api_header_file "${CMAKE_CURRENT_SOURCE_DIR}/api/${header_file}")
+  list(APPEND Z3_FULL_PATH_API_HEADER_FILES_TO_SCAN "${full_path_api_header_file}")
+  if (NOT EXISTS "${full_path_api_header_file}")
+    message(FATAL_ERROR "API header file \"${full_path_api_header_file}\" does not exist")
+  endif()
+endforeach()
+
+################################################################################
+# Traverse directories each adding a Z3 component
+################################################################################
 # I'm duplicating the order in ``mk_project.py`` for now to help us keep
 # the build systems in sync.
 #
 # The components in these directory explicitly declare their dependencies so
 # you may be able to re-order some of these directories but an error will be
-# raised if you try to declare a component is depedent on another component
+# raised if you try to declare a component is dependent on another component
 # that has not yet been declared.
 add_subdirectory(util)
 add_subdirectory(math/polynomial)
@@ -138,6 +167,7 @@ install(TARGETS libz3
   ARCHIVE DESTINATION "${Z3_INSTALL_LIB_DIR}"
   PUBLIC_HEADER DESTINATION "${Z3_INSTALL_INCLUDE_DIR}"
 )
+
 ################################################################################
 # Z3 executable
 ################################################################################
diff --git a/src/api/CMakeLists.txt b/src/api/CMakeLists.txt
index 506b28cb3..b5a111a25 100644
--- a/src/api/CMakeLists.txt
+++ b/src/api/CMakeLists.txt
@@ -1,14 +1,3 @@
-set(api_header_files_to_scan
-  z3_api.h
-  z3_ast_containers.h
-  z3_algebraic.h
-  z3_polynomial.h
-  z3_rcf.h
-  z3_fixedpoint.h
-  z3_optimization.h
-  z3_interp.h
-  z3_fpa.h
-)
 set(generated_files
   api_commands.cpp
   api_log_macros.cpp
@@ -23,10 +12,6 @@ foreach (gen_file ${generated_files})
   endif()
 endforeach()
 
-set(full_path_api_header_files_to_scan "")
-foreach (header_file ${api_header_files_to_scan})
-  list(APPEND full_path_api_header_files_to_scan "${CMAKE_CURRENT_SOURCE_DIR}/${header_file}")
-endforeach()
 set(full_path_generated_files "")
 foreach (gen_file ${generated_files})
   list(APPEND full_path_generated_files "${CMAKE_CURRENT_BINARY_DIR}/${gen_file}")
@@ -36,12 +21,12 @@ add_custom_command(OUTPUT ${generated_files}
   COMMAND "${PYTHON_EXECUTABLE}"
   "${CMAKE_SOURCE_DIR}/scripts/update_api.py"
   "${CMAKE_CURRENT_BINARY_DIR}"
-  ${full_path_api_header_files_to_scan}
+  ${Z3_FULL_PATH_API_HEADER_FILES_TO_SCAN}
   DEPENDS "${CMAKE_SOURCE_DIR}/scripts/update_api.py"
           "${CMAKE_SOURCE_DIR}/scripts/mk_util.py"
-          ${full_path_api_header_files_to_scan}
+          ${Z3_FULL_PATH_API_HEADER_FILES_TO_SCAN}
   COMMENT "Generating ${generated_files}"
-  USES_TERMINAL
+  ${ADD_CUSTOM_COMMAND_USES_TERMINAL_ARG}
   VERBATIM
 )