diff --git a/Applications/Debugger/main.cpp b/Applications/Debugger/main.cpp
index 893126d6e2e..3bba792f578 100644
--- a/Applications/Debugger/main.cpp
+++ b/Applications/Debugger/main.cpp
@@ -30,7 +30,6 @@
 #include <AK/LogStream.h>
 #include <AK/StringBuilder.h>
 #include <AK/kmalloc.h>
-#include <LibC/sys/arch/i386/regs.h>
 #include <LibCore/File.h>
 #include <LibDebug/DebugInfo.h>
 #include <LibDebug/DebugSession.h>
@@ -41,6 +40,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/arch/i386/regs.h>
 #include <unistd.h>
 
 static Line::Editor editor {};
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0d0acb5f54f..3ea505f9b01 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -52,6 +52,7 @@ function(serenity_libc target_name fs_name)
     add_library(${target_name} ${SOURCES})
     install(TARGETS ${target_name} ARCHIVE DESTINATION usr/lib)
     set_target_properties(${target_name} PROPERTIES OUTPUT_NAME ${fs_name})
+    target_include_directories(${target_name} SYSTEM PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
     target_link_directories(LibC PUBLIC ${CMAKE_CURRENT_BINARY_DIR})
 endfunction()
 
@@ -101,8 +102,9 @@ set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Os -Wno-sized-deallocation -fno-sized-d
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DDEBUG -DSANITIZE_PTRS")
 add_link_options(--sysroot ${CMAKE_BINARY_DIR}/Root)
 
-include_directories(Libraries/LibC)
+# Source directory relative service headers
 include_directories(Services)
+# Generated Service/Library Headers
 include_directories(${CMAKE_CURRENT_BINARY_DIR}/Services)
 include_directories(${CMAKE_CURRENT_BINARY_DIR}/Libraries)
 
diff --git a/Kernel/CMakeLists.txt b/Kernel/CMakeLists.txt
index 6ef6d24296e..f6684df8ce1 100644
--- a/Kernel/CMakeLists.txt
+++ b/Kernel/CMakeLists.txt
@@ -161,6 +161,9 @@ if (${CMAKE_HOST_SYSTEM_NAME} MATCHES SerenityOS)
 else()
     include_directories(../Toolchain/Local/i686-pc-serenity/include/c++/10.1.0/)
     include_directories(../Toolchain/Local/i686-pc-serenity/include/c++/10.1.0/i686-pc-serenity/)
+    # FIXME: Many files include <LibC/sys/ioctl_numbers.h> and <LibC/errno_numbers.h>
+    #     With -nostdinc, this makes it interesting to include these headers properly
+    include_directories(../Libraries/LibC)
 endif()
 
 add_executable(Kernel ${SOURCES})
diff --git a/Libraries/LibC/CMakeLists.txt b/Libraries/LibC/CMakeLists.txt
index d5e94d1b960..feee96aa971 100644
--- a/Libraries/LibC/CMakeLists.txt
+++ b/Libraries/LibC/CMakeLists.txt
@@ -52,6 +52,8 @@ file(GLOB ELF_SOURCES "../LibELF/*.cpp")
 set(ELF_SOURCES ${ELF_SOURCES} ../LibELF/Arch/i386/plt_trampoline.S)
 
 add_library(crt0 STATIC crt0.cpp)
+# We need include headers from LibC in crt0. namely, <assert.h>
+target_include_directories(crt0 PRIVATE ${CMAKE_CURRENT_SOURCE_DIR})
 add_custom_command(
     TARGET crt0
     COMMAND install -D $<TARGET_OBJECTS:crt0> ${CMAKE_INSTALL_PREFIX}/usr/lib/crt0.o
diff --git a/Libraries/LibDebug/DebugSession.h b/Libraries/LibDebug/DebugSession.h
index 20a549f7771..95687926c37 100644
--- a/Libraries/LibDebug/DebugSession.h
+++ b/Libraries/LibDebug/DebugSession.h
@@ -33,11 +33,11 @@
 #include <AK/Optional.h>
 #include <AK/OwnPtr.h>
 #include <AK/String.h>
-#include <LibC/sys/arch/i386/regs.h>
 #include <LibDebug/DebugInfo.h>
 #include <LibELF/Loader.h>
 #include <signal.h>
 #include <stdio.h>
+#include <sys/arch/i386/regs.h>
 #include <sys/ptrace.h>
 #include <sys/wait.h>
 #include <unistd.h>
diff --git a/Libraries/LibM/CMakeLists.txt b/Libraries/LibM/CMakeLists.txt
index 7ed9959738b..c9bf4dd6552 100644
--- a/Libraries/LibM/CMakeLists.txt
+++ b/Libraries/LibM/CMakeLists.txt
@@ -3,5 +3,4 @@ set(SOURCES
 )
 
 serenity_libc(LibM m)
-target_include_directories(LibM PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
 target_link_libraries(LibM LibC)
diff --git a/Libraries/LibM/math.cpp b/Libraries/LibM/math.cpp
index 021993e9d4b..26e96422962 100644
--- a/Libraries/LibM/math.cpp
+++ b/Libraries/LibM/math.cpp
@@ -24,8 +24,8 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#include <LibC/assert.h>
-#include <LibM/math.h>
+#include <assert.h>
+#include <math.h>
 #include <stdint.h>
 #include <stdlib.h>
 
diff --git a/Libraries/LibPthread/CMakeLists.txt b/Libraries/LibPthread/CMakeLists.txt
index 7a668f06848..3fd2e1d7020 100644
--- a/Libraries/LibPthread/CMakeLists.txt
+++ b/Libraries/LibPthread/CMakeLists.txt
@@ -4,4 +4,3 @@ set(SOURCES
 
 serenity_libc(LibPthread pthread)
 target_link_libraries(LibPthread LibC)
-target_include_directories(LibPthread PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
diff --git a/Userland/functrace.cpp b/Userland/functrace.cpp
index 877a7aa6012..4e30d12fd88 100644
--- a/Userland/functrace.cpp
+++ b/Userland/functrace.cpp
@@ -33,7 +33,6 @@
 #include <AK/StringBuilder.h>
 #include <AK/kmalloc.h>
 #include <Kernel/Syscall.h>
-#include <LibC/sys/arch/i386/regs.h>
 #include <LibCore/File.h>
 #include <LibDebug/DebugSession.h>
 #include <LibELF/Image.h>
@@ -44,6 +43,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/arch/i386/regs.h>
 #include <unistd.h>
 
 static int usage()
diff --git a/Userland/strace.cpp b/Userland/strace.cpp
index b6687cfa589..58e018d5754 100644
--- a/Userland/strace.cpp
+++ b/Userland/strace.cpp
@@ -28,11 +28,11 @@
 #include <AK/LogStream.h>
 #include <AK/Types.h>
 #include <Kernel/Syscall.h>
-#include <LibC/sys/arch/i386/regs.h>
 #include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/arch/i386/regs.h>
 #include <sys/ptrace.h>
 #include <sys/wait.h>
 #include <unistd.h>
diff --git a/Userland/test-crypto.cpp b/Userland/test-crypto.cpp
index 4f22de89c15..2b0fb8b9f58 100644
--- a/Userland/test-crypto.cpp
+++ b/Userland/test-crypto.cpp
@@ -24,7 +24,6 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#include <LibC/limits.h>
 #include <LibCore/ArgsParser.h>
 #include <LibCore/EventLoop.h>
 #include <LibCore/File.h>
@@ -37,6 +36,7 @@
 #include <LibCrypto/PK/RSA.h>
 #include <LibLine/Editor.h>
 #include <LibTLS/TLSv12.h>
+#include <limits.h>
 #include <stdio.h>
 #include <time.h>