diff --git a/library/CMakeLists.txt b/library/CMakeLists.txt
index c551ee557..8fd959c1a 100644
--- a/library/CMakeLists.txt
+++ b/library/CMakeLists.txt
@@ -192,6 +192,11 @@ if(USE_SHARED_MBEDTLS_LIBRARY)
 endif(USE_SHARED_MBEDTLS_LIBRARY)
 
 foreach(target IN LISTS target_libraries)
+    # Include public header files from /include and other directories
+    # declared by /3rdparty/**/CMakeLists.txt. Include private header files
+    # from /library and others declared by /3rdparty/**/CMakeLists.txt.
+    # /library needs to be listed explicitly when building .c files outside
+    # of /library (which currently means: under /3rdparty).
     target_include_directories(${target}
         PUBLIC ${MBEDTLS_DIR}/include/
         PUBLIC ${thirdparty_inc_public}
diff --git a/library/Makefile b/library/Makefile
index 801304bbe..20a598481 100644
--- a/library/Makefile
+++ b/library/Makefile
@@ -5,6 +5,10 @@ CFLAGS	?= -O2
 WARNING_CFLAGS ?=  -Wall -Wextra
 LDFLAGS ?=
 
+# Include ../include for public headers and . for private headers.
+# Note that . needs to be included explicitly for the sake of library
+# files that are not in the /library directory (which currently means
+# under /3rdparty).
 LOCAL_CFLAGS = $(WARNING_CFLAGS) -I. -I../include -D_FILE_OFFSET_BITS=64
 LOCAL_LDFLAGS =
 
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 8a74c6bfb..cc6866309 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -48,6 +48,10 @@ function(add_test_suite suite_name)
 
     add_executable(test_suite_${data_name} test_suite_${data_name}.c $<TARGET_OBJECTS:mbedtls_test>)
     target_link_libraries(test_suite_${data_name} ${libs})
+    # Include test-specific header files from ./include and private header
+    # files (used by some invasive tests) from ../library. Public header
+    # files are automatically included because the library targets declare
+    # them as PUBLIC.
     target_include_directories(test_suite_${data_name}
         PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include
         PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/../library)
diff --git a/tests/Makefile b/tests/Makefile
index 80c84fa19..ffa4812bd 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -6,6 +6,9 @@ CFLAGS	?= -O2
 WARNING_CFLAGS ?= -Wall -Wextra
 LDFLAGS ?=
 
+# Include public header files from ../include, test-specific header files
+# from ./include, and private header files (used by some invasive tests)
+# from ../library.
 LOCAL_CFLAGS = $(WARNING_CFLAGS) -I./include -I../include -I../library -D_FILE_OFFSET_BITS=64
 LOCAL_LDFLAGS = -L../library			\
 		-lmbedtls$(SHARED_SUFFIX)	\