Index: lib/MC/MCObjectFileInfo.cpp
===================================================================
--- lib/MC/MCObjectFileInfo.cpp
+++ lib/MC/MCObjectFileInfo.cpp
@@ -599,6 +599,13 @@
   // used to indicate to the linker that the text segment contains thumb instructions
   // and to set the ISA selection bit for calls accordingly.
   const bool IsThumb = T.getArch() == Triple::thumb;
+  // Windows on ARM is thumb only, and thus needs to set the IMAGE_SCN_MEM_16BIT
+  // flag. When the assembler is invoked via the clang driver, the triple is
+  // always set to arm-* (since the assembler always should start in ARM mode).
+  // Check for windows here, since we can't easily check the attributes of the
+  // contained individual functions here.
+  const bool IsWinARM = (T.isOSWindows() &&
+                        (T.getArch() == Triple::arm || T.getArch() == Triple::thumb));
 
   CommDirectiveSupportsAlignment = true;
 
@@ -609,7 +616,7 @@
       SectionKind::getBSS());
   TextSection = Ctx->getCOFFSection(
       ".text",
-      (IsThumb ? COFF::IMAGE_SCN_MEM_16BIT : (COFF::SectionCharacteristics)0) |
+      ((IsThumb || IsWinARM) ? COFF::IMAGE_SCN_MEM_16BIT : (COFF::SectionCharacteristics)0) |
           COFF::IMAGE_SCN_CNT_CODE | COFF::IMAGE_SCN_MEM_EXECUTE |
           COFF::IMAGE_SCN_MEM_READ,
       SectionKind::getText());
Index: test/MC/ARM/Windows/thumb-attributes.s
===================================================================
--- /dev/null
+++ test/MC/ARM/Windows/thumb-attributes.s
@@ -0,0 +1,22 @@
+@ RUN: llvm-mc -triple armv7-windows-itanium -filetype obj -o - %s \
+@ RUN:   | llvm-readobj -s - | FileCheck %s
+
+	.syntax unified
+	.thumb
+
+	.text
+
+	.global function
+	.thumb_func
+function:
+	bx lr
+
+@ CHECK: Sections [
+@ CHECK:   Section {
+@ CHECK:     Name: .text
+@ CHECK:     Characteristics [
+@ CHECK-DAG:   IMAGE_SCN_CNT_CODE
+@ CHECK-DAG:   IMAGE_SCN_MEM_16BIT
+@ CHECK:     ]
+@ CHECK:   }
+@ CHECK: ]