diff --git a/core/fpdfapi/cmaps/CNS1/cmaps_cns1.h b/core/fpdfapi/cmaps/CNS1/cmaps_cns1.h
index 64f6b8b..0660c76 100644
--- a/core/fpdfapi/cmaps/CNS1/cmaps_cns1.h
+++ b/core/fpdfapi/cmaps/CNS1/cmaps_cns1.h
@@ -7,6 +7,8 @@
 #ifndef CORE_FPDFAPI_CMAPS_CNS1_CMAPS_CNS1_H_
 #define CORE_FPDFAPI_CMAPS_CNS1_CMAPS_CNS1_H_
 
+#include <stddef.h>
+
 #include "core/fpdfapi/cmaps/fpdf_cmaps.h"
 
 extern const uint16_t g_FXCMAP_B5pc_H_0[];
diff --git a/core/fpdfapi/cmaps/GB1/cmaps_gb1.h b/core/fpdfapi/cmaps/GB1/cmaps_gb1.h
index 7873f64..61b50c8 100644
--- a/core/fpdfapi/cmaps/GB1/cmaps_gb1.h
+++ b/core/fpdfapi/cmaps/GB1/cmaps_gb1.h
@@ -7,6 +7,8 @@
 #ifndef CORE_FPDFAPI_CMAPS_GB1_CMAPS_GB1_H_
 #define CORE_FPDFAPI_CMAPS_GB1_CMAPS_GB1_H_
 
+#include <stddef.h>
+
 #include "core/fpdfapi/cmaps/fpdf_cmaps.h"
 
 extern const uint16_t g_FXCMAP_GB_EUC_H_0[];
diff --git a/core/fpdfapi/cmaps/Japan1/cmaps_japan1.h b/core/fpdfapi/cmaps/Japan1/cmaps_japan1.h
index 267a9fc..f0b3014 100644
--- a/core/fpdfapi/cmaps/Japan1/cmaps_japan1.h
+++ b/core/fpdfapi/cmaps/Japan1/cmaps_japan1.h
@@ -7,6 +7,8 @@
 #ifndef CORE_FPDFAPI_CMAPS_JAPAN1_CMAPS_JAPAN1_H_
 #define CORE_FPDFAPI_CMAPS_JAPAN1_CMAPS_JAPAN1_H_
 
+#include <stddef.h>
+
 #include "core/fpdfapi/cmaps/fpdf_cmaps.h"
 
 extern const uint16_t g_FXCMAP_83pv_RKSJ_H_1[];
diff --git a/core/fpdfapi/cmaps/Korea1/cmaps_korea1.h b/core/fpdfapi/cmaps/Korea1/cmaps_korea1.h
index d54d156..f132824 100644
--- a/core/fpdfapi/cmaps/Korea1/cmaps_korea1.h
+++ b/core/fpdfapi/cmaps/Korea1/cmaps_korea1.h
@@ -7,6 +7,8 @@
 #ifndef CORE_FPDFAPI_CMAPS_KOREA1_CMAPS_KOREA1_H_
 #define CORE_FPDFAPI_CMAPS_KOREA1_CMAPS_KOREA1_H_
 
+#include <stddef.h>
+
 #include "core/fpdfapi/cmaps/fpdf_cmaps.h"
 
 extern const uint16_t g_FXCMAP_KSC_EUC_H_0[];
diff --git a/core/fpdfapi/cmaps/fpdf_cmaps.h b/core/fpdfapi/cmaps/fpdf_cmaps.h
index de8800c..38b8b4f 100644
--- a/core/fpdfapi/cmaps/fpdf_cmaps.h
+++ b/core/fpdfapi/cmaps/fpdf_cmaps.h
@@ -9,8 +9,6 @@
 
 #include <stdint.h>
 
-#include "core/fxcrt/fx_string.h"
-
 struct FXCMAP_DWordCIDMap {
   uint16_t m_HiWord;
   uint16_t m_LoWordLow;