diff --git a/core/fxge/BUILD.gn b/core/fxge/BUILD.gn
index 8ccaf68..7dafd7d 100644
--- a/core/fxge/BUILD.gn
+++ b/core/fxge/BUILD.gn
@@ -10,6 +10,8 @@
   visibility = [ ":*" ]
   if (is_clang) {
     cflags = [
+      "-Wshorten-64-to-32",
+
       # http://code.google.com/p/pdfium/issues/detail?id=188
       "-Wno-switch",
     ]
diff --git a/core/fxge/cfx_face.cpp b/core/fxge/cfx_face.cpp
index 1946843..d838a4b 100644
--- a/core/fxge/cfx_face.cpp
+++ b/core/fxge/cfx_face.cpp
@@ -5,6 +5,7 @@
 #include "core/fxge/cfx_face.h"
 
 #include "third_party/base/check.h"
+#include "third_party/base/numerics/safe_conversions.h"
 
 // static
 RetainPtr<CFX_Face> CFX_Face::New(FT_Library library,
@@ -12,8 +13,9 @@
                                   pdfium::span<const FT_Byte> data,
                                   FT_Long face_index) {
   FXFT_FaceRec* pRec = nullptr;
-  if (FT_New_Memory_Face(library, data.data(), data.size(), face_index,
-                         &pRec) != 0) {
+  if (FT_New_Memory_Face(library, data.data(),
+                         pdfium::base::checked_cast<FT_Long>(data.size()),
+                         face_index, &pRec) != 0) {
     return nullptr;
   }
   return pdfium::WrapRetain(new CFX_Face(pRec, pDesc));
diff --git a/core/fxge/skia/fx_skia_device.cpp b/core/fxge/skia/fx_skia_device.cpp
index 2af6275..5688660 100644
--- a/core/fxge/skia/fx_skia_device.cpp
+++ b/core/fxge/skia/fx_skia_device.cpp
@@ -39,6 +39,7 @@
 #include "third_party/base/check_op.h"
 #include "third_party/base/cxx17_backports.h"
 #include "third_party/base/notreached.h"
+#include "third_party/base/numerics/safe_conversions.h"
 #include "third_party/base/ptr_util.h"
 #include "third_party/base/span.h"
 #include "third_party/skia/include/core/SkBitmap.h"
@@ -490,8 +491,8 @@
   float boundsStart = pFunc->GetDomain(0);
 
   const auto& subFunctions = pFunc->GetSubFunctions();
-  int subFunctionCount = subFunctions.size();
-  for (int i = 0; i < subFunctionCount; ++i) {
+  size_t subFunctionCount = subFunctions.size();
+  for (size_t i = 0; i < subFunctionCount; ++i) {
     const CPDF_ExpIntFunc* pSubFunc = subFunctions[i]->ToExpIntFunc();
     if (!pSubFunc)
       return false;
@@ -1620,7 +1621,8 @@
       intervals[i * 2 + 1] = off;
     }
     spaint->setPathEffect(SkDashPathEffect::Make(
-        intervals.data(), intervals.size(), pGraphState->m_DashPhase));
+        intervals.data(), pdfium::base::checked_cast<int>(intervals.size()),
+        pGraphState->m_DashPhase));
   }
   spaint->setStyle(SkPaint::kStroke_Style);
   spaint->setAntiAlias(!m_FillOptions.aliased_path);
@@ -2176,7 +2178,7 @@
   }
   const std::vector<std::unique_ptr<CPDF_Function>>& pFuncs =
       pPattern->GetFuncs();
-  int nFuncs = pFuncs.size();
+  size_t nFuncs = pFuncs.size();
   if (nFuncs > 1)  // TODO(caryclark) remove this restriction
     return false;
   const CPDF_Dictionary* pDict = pPattern->GetShadingObject()->GetDict();
@@ -2187,7 +2189,7 @@
   // yet.)
   SkTDArray<SkColor> skColors;
   SkTDArray<SkScalar> skPos;
-  for (int j = 0; j < nFuncs; j++) {
+  for (size_t j = 0; j < nFuncs; j++) {
     if (!pFuncs[j])
       continue;