diff --git a/appveyor.yml b/appveyor.yml
index fc5e44e7..ba3f8921 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -6,12 +6,14 @@ branches:
 
 platform:
   - x86
+  - x64
 
 init:
   - git config --global core.autocrlf false
 
 install:
-  - call "C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\vcvarsall.bat" x86
+  - IF "%PLATFORM%" == "x86" (call "C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvars32.bat")
+  - IF "%PLATFORM%" == "x64" (call "C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvars64.bat")
   - script\configure.cmd
   - script\fetch-fixtures.cmd
 
@@ -21,4 +23,4 @@ test_script:
 build: off
 
 cache:
-  - test\fixtures\grammars
\ No newline at end of file
+  - test\fixtures\grammars
diff --git a/project.gyp b/project.gyp
index 38f6e551..b9818861 100644
--- a/project.gyp
+++ b/project.gyp
@@ -162,5 +162,13 @@
         '-Wno-unused-parameter'
       ],
     },
+
+    # For 64-bit builds on appveyor, we need to explicitly tell gyp
+    # to generate an x64 target in the MSVS project file.
+    'conditions': [
+      ['"<!(echo %PLATFORM%)" == "x64"', {
+        'msvs_configuration_platform': 'x64',
+      }]
+    ]
   }
 }
diff --git a/tests.gyp b/tests.gyp
index ed97c3e4..a8f3a596 100644
--- a/tests.gyp
+++ b/tests.gyp
@@ -21,6 +21,7 @@
         'test/helpers/stderr_logger.cc',
       ],
     },
+
     {
       'target_name': 'tests',
       'default_configuration': 'Test',
@@ -97,12 +98,21 @@
 
   'target_defaults': {
     'configurations': {'Test': {}, 'Release': {}},
+
     'cflags_cc': ['-std=c++14'],
+
     'conditions': [
       ['OS=="linux"', {
         'libraries': ['-ldl', '-lpthread'],
+      }],
+
+      # For 64-bit builds on appveyor, we need to explicitly tell gyp
+      # to generate an x64 target in the MSVS project file.
+      ['"<!(echo %PLATFORM%)" == "x64"', {
+        'msvs_configuration_platform': 'x64',
       }]
     ],
+
     'xcode_settings': {
       'CLANG_CXX_LANGUAGE_STANDARD': 'c++14',
       'ALWAYS_SEARCH_USER_PATHS': 'NO',