diff --git a/tools/gpu/FenceSync.h b/tools/gpu/FenceSync.h
index c3f1182..8f2bbe2 100644
--- a/tools/gpu/FenceSync.h
+++ b/tools/gpu/FenceSync.h
@@ -12,7 +12,7 @@
 
 namespace sk_gpu_test {
 
-using PlatformFence = intptr_t;
+using PlatformFence = uint64_t;
 static constexpr PlatformFence kInvalidPlatformFence = 0;
 
 /*
diff --git a/tools/gpu/gl/GLTestContext.cpp b/tools/gpu/gl/GLTestContext.cpp
index 1d53bbc..1b077d5 100644
--- a/tools/gpu/gl/GLTestContext.cpp
+++ b/tools/gpu/gl/GLTestContext.cpp
@@ -28,6 +28,7 @@
     static constexpr GrGLbitfield GL_SYNC_FLUSH_COMMANDS_BIT = 0x00000001;
 
     typedef struct __GLsync *GLsync;
+    GR_STATIC_ASSERT(sizeof(GLsync) <= sizeof(sk_gpu_test::PlatformFence));
 
     typedef GLsync (GR_GL_FUNCTION_TYPE* GLFenceSyncProc) (GrGLenum, GrGLbitfield);
     typedef GrGLenum (GR_GL_FUNCTION_TYPE* GLClientWaitSyncProc) (GLsync, GrGLbitfield, GrGLuint64);
diff --git a/tools/gpu/gl/egl/CreatePlatformGLTestContext_egl.cpp b/tools/gpu/gl/egl/CreatePlatformGLTestContext_egl.cpp
index 8fdd3fe..06bd70f 100644
--- a/tools/gpu/gl/egl/CreatePlatformGLTestContext_egl.cpp
+++ b/tools/gpu/gl/egl/CreatePlatformGLTestContext_egl.cpp
@@ -320,6 +320,8 @@
     eglDestroySyncKHR(fDisplay, eglsync);
 }
 
+GR_STATIC_ASSERT(sizeof(EGLSyncKHR) <= sizeof(sk_gpu_test::PlatformFence));
+
 }  // anonymous namespace
 
 namespace sk_gpu_test {
@@ -337,4 +339,3 @@
     return ctx;
 }
 }  // namespace sk_gpu_test
-
diff --git a/tools/gpu/vk/VkTestContext.cpp b/tools/gpu/vk/VkTestContext.cpp
index c1a2f8a..a76a361 100644
--- a/tools/gpu/vk/VkTestContext.cpp
+++ b/tools/gpu/vk/VkTestContext.cpp
@@ -103,6 +103,8 @@
     typedef sk_gpu_test::FenceSync INHERITED;
 };
 
+GR_STATIC_ASSERT(sizeof(VkFence) <= sizeof(sk_gpu_test::PlatformFence));
+
 // TODO: Implement swap buffers and finish
 class VkTestContextImpl : public sk_gpu_test::VkTestContext {
 public: