diff --git a/cmake/modules/SwiftSource.cmake b/cmake/modules/SwiftSource.cmake
index 5b3154e911c78..bd581b17dc677 100644
--- a/cmake/modules/SwiftSource.cmake
+++ b/cmake/modules/SwiftSource.cmake
@@ -451,12 +451,21 @@ function(_compile_swift_files
 
   # Then we can compile both the object files and the swiftmodule files
   # in parallel in this target for the object file, and ...
+
+  # Windows doesn't support long command line paths, of 8191 chars or over.
+  # We need to work around this by avoiding long command line arguments. This can be
+  # achieved by writing the list of file paths to a file, then reading that list
+  # in the Python script.
+  string(RANDOM file_name)
+  set(file_path "${CMAKE_CURRENT_BINARY_DIR}/${file_name}.txt")
+  file(WRITE "${file_path}" "${source_files}")
+  
   add_custom_command_target(
       dependency_target
       COMMAND
-        "${PYTHON_EXECUTABLE}" "${line_directive_tool}" "${source_files}" --
+        "${PYTHON_EXECUTABLE}" "${line_directive_tool}" "@${file_path}" --
         "${swift_compiler_tool}" "${main_command}" ${swift_flags}
-        ${output_option} ${embed_bitcode_option} "${source_files}"
+        ${output_option} ${embed_bitcode_option} "@${file_path}"
       ${command_touch_standard_outputs}
       OUTPUT ${standard_outputs}
       DEPENDS
@@ -485,9 +494,9 @@ function(_compile_swift_files
     add_custom_command_target(
         module_dependency_target
         COMMAND
-          "${PYTHON_EXECUTABLE}" "${line_directive_tool}" "${source_files}" --
+          "${PYTHON_EXECUTABLE}" "${line_directive_tool}" "@${file_path}" --
           "${swift_compiler_tool}" "-emit-module" "-o" "${module_file}" ${swift_flags}
-          "${source_files}"
+          "@${file_path}"
         ${command_touch_module_outputs}
         OUTPUT ${module_outputs}
         DEPENDS
@@ -502,9 +511,9 @@ function(_compile_swift_files
     add_custom_command_target(
         sib_dependency_target
         COMMAND
-          "${PYTHON_EXECUTABLE}" "${line_directive_tool}" "${source_files}" --
+          "${PYTHON_EXECUTABLE}" "${line_directive_tool}" "@${file_path}" --
           "${swift_compiler_tool}" "-emit-sib" "-o" "${sib_file}" ${swift_flags} -Onone
-          "${source_files}"
+          "@${file_path}"
         ${command_touch_sib_outputs}
         OUTPUT ${sib_outputs}
         DEPENDS
@@ -518,9 +527,9 @@ function(_compile_swift_files
     add_custom_command_target(
         sibopt_dependency_target
         COMMAND
-          "${PYTHON_EXECUTABLE}" "${line_directive_tool}" "${source_files}" --
+          "${PYTHON_EXECUTABLE}" "${line_directive_tool}" "@${file_path}" --
           "${swift_compiler_tool}" "-emit-sib" "-o" "${sibopt_file}" ${swift_flags} -O
-          "${source_files}"
+          "@${file_path}"
         ${command_touch_sibopt_outputs}
         OUTPUT ${sibopt_outputs}
         DEPENDS
@@ -535,9 +544,9 @@ function(_compile_swift_files
     add_custom_command_target(
         sibgen_dependency_target
         COMMAND
-          "${PYTHON_EXECUTABLE}" "${line_directive_tool}" "${source_files}" --
+          "${PYTHON_EXECUTABLE}" "${line_directive_tool}" "@${file_path}" --
           "${swift_compiler_tool}" "-emit-sibgen" "-o" "${sibgen_file}" ${swift_flags}
-          "${source_files}"
+          "@${file_path}"
         ${command_touch_sibgen_outputs}
         OUTPUT ${sibgen_outputs}
         DEPENDS
diff --git a/utils/line-directive b/utils/line-directive
index 49166e29dbdee..07e6c5d2965df 100755
--- a/utils/line-directive
+++ b/utils/line-directive
@@ -154,6 +154,21 @@ def map_line_from_source_file(source_filename, source_line_num, target_filename)
             return result + 1
     raise RuntimeError("line not found")
 
+def read_response_file(file_path):
+    with open(file_path, 'r') as files:
+        return filter(None, files.read().split(';'))
+
+def expand_response_files(files):
+    expanded_files = []
+    for file_path in files:
+        # Read a list of files from a response file.
+        if file_path[0] == '@':
+            expanded_files.extend(read_response_file(file_path[1:]))
+        else:
+            expanded_files.append(file_path)
+
+    return expanded_files
+
 def run():
     """Simulate a couple of gyb-generated files
 
@@ -243,7 +258,7 @@ def run():
         print(map_line_from_source_file(source_file, source_line, target_file))
     else:
         dashes = sys.argv.index('--')
-        sources = sys.argv[1:dashes]
+        sources = expand_response_files(sys.argv[1:dashes])
 
         # The first argument of command_args is the process to open.
         # subprocess.Popen doesn't normalize arguments. This means that trying
@@ -252,7 +267,7 @@ def run():
         # to the Win32 CreateProcess API. Unix systems handle non-normalized
         # paths, so don't have this problem.
         # Arguments passed to the process are normalized by the process.
-        command_args = sys.argv[dashes + 1:]
+        command_args = expand_response_files(sys.argv[dashes + 1:])
         command_args[0] = os.path.normpath(command_args[0])
 
         command = subprocess.Popen(