diff --git a/include/llvm/MC/MCSectionELF.h b/include/llvm/MC/MCSectionELF.h
index 5de0bf58fe0..f97ab167118 100644
--- a/include/llvm/MC/MCSectionELF.h
+++ b/include/llvm/MC/MCSectionELF.h
@@ -189,6 +189,10 @@ public:
     return S->getVariant() == SV_ELF;
   }
   static bool classof(const MCSectionELF *) { return true; }
+
+  // Return the entry size for sections with fixed-width data.
+  static unsigned DetermineEntrySize(SectionKind Kind);
+
 };
 
 } // end namespace llvm
diff --git a/lib/MC/MCContext.cpp b/lib/MC/MCContext.cpp
index e5586a0d7c3..1e65f877924 100644
--- a/lib/MC/MCContext.cpp
+++ b/lib/MC/MCContext.cpp
@@ -160,6 +160,10 @@ getELFSection(StringRef Section, unsigned Type, unsigned Flags,
   StringMapEntry<const MCSectionELF*> &Entry = Map.GetOrCreateValue(Section);
   if (Entry.getValue()) return Entry.getValue();
   
+  // Possibly refine the entry size first.
+  if (!EntrySize) {
+    EntrySize = MCSectionELF::DetermineEntrySize(Kind);
+  }
   MCSectionELF *Result = new (*this) MCSectionELF(Entry.getKey(), Type, Flags,
                                                   Kind, IsExplicit, EntrySize);
   Entry.setValue(Result);
diff --git a/lib/MC/MCSectionELF.cpp b/lib/MC/MCSectionELF.cpp
index a7599de1b7b..ef935d0c64b 100644
--- a/lib/MC/MCSectionELF.cpp
+++ b/lib/MC/MCSectionELF.cpp
@@ -104,17 +104,8 @@ void MCSectionELF::PrintSwitchToSection(const MCAsmInfo &MAI,
     else if (Type == MCSectionELF::SHT_PROGBITS)
       OS << "progbits";
   
-    if (getKind().isMergeable1ByteCString()) {
-      OS << ",1";
-    } else if (getKind().isMergeable2ByteCString()) {
-      OS << ",2";
-    } else if (getKind().isMergeable4ByteCString() || 
-               getKind().isMergeableConst4()) {
-      OS << ",4";
-    } else if (getKind().isMergeableConst8()) {
-      OS << ",8";
-    } else if (getKind().isMergeableConst16()) {
-      OS << ",16";
+    if (EntrySize) {
+      OS << "," << EntrySize;
     }
   }
   
@@ -132,4 +123,12 @@ bool MCSectionELF::HasCommonSymbols() const {
   return false;
 }
 
-
+unsigned MCSectionELF::DetermineEntrySize(SectionKind Kind) {
+  if (Kind.isMergeable1ByteCString()) return 1;
+  if (Kind.isMergeable2ByteCString()) return 2;
+  if (Kind.isMergeable4ByteCString()) return 4;
+  if (Kind.isMergeableConst4())       return 4;
+  if (Kind.isMergeableConst8())       return 8;
+  if (Kind.isMergeableConst16())      return 16;
+  return 0;
+}
diff --git a/test/MC/ELF/entsize.ll b/test/MC/ELF/entsize.ll
new file mode 100644
index 00000000000..f8290d122d8
--- /dev/null
+++ b/test/MC/ELF/entsize.ll
@@ -0,0 +1,44 @@
+; RUN: llc -filetype=obj -mtriple x86_64-pc-linux-gnu %s -o - | elf-dump | FileCheck -check-prefix=64 %s
+
+; Test that constant mergeable strings have sh_entsize set.
+
+@.str1 = private constant [6 x i8] c"tring\00"
+@.str2 = private constant [7 x i8] c"String\00"
+@.c8a = private constant [1 x i64] [i64 42]
+@.c8b = private constant [1 x i64] [i64 42]
+
+define i32 @main() nounwind {
+  %1 = call i32 @puts(i8* getelementptr inbounds ([6 x i8]* @.str1, i32 0, i32 0))
+  %2 = call i32 @puts(i8* getelementptr inbounds ([7 x i8]* @.str2, i32 0, i32 0))
+  call void @foo(i64* getelementptr inbounds ([1 x i64]* @.c8a, i32 0, i32 0))
+  call void @foo(i64* getelementptr inbounds ([1 x i64]* @.c8b, i32 0, i32 0))
+  ret i32 0
+}
+
+declare i32 @puts(i8* nocapture) nounwind
+declare void @foo(i64* nocapture) nounwind
+
+;;;;;
+
+; 64: (('sh_name', 7) # '.rodata.str1.1'
+; 64-NEXT:   ('sh_type', 1)
+; 64-NEXT:   ('sh_flags', 50)
+; 64-NEXT:   ('sh_addr',
+; 64-NEXT:   ('sh_offset',
+; 64-NEXT:   ('sh_size', 13)
+; 64-NEXT:   ('sh_link',
+; 64-NEXT:   ('sh_info',
+; 64-NEXT:   ('sh_addralign', 1)
+; 64-NEXT:   ('sh_entsize', 1)
+
+; 64: (('sh_name', 22) # '.rodata.cst8'
+; 64-NEXT:   ('sh_type', 1)
+; 64-NEXT:   ('sh_flags', 18)
+; 64-NEXT:   ('sh_addr',
+; 64-NEXT:   ('sh_offset',
+; 64-NEXT:   ('sh_size', 16)
+; 64-NEXT:   ('sh_link',
+; 64-NEXT:   ('sh_info',
+; 64-NEXT:   ('sh_addralign', 8)
+; 64-NEXT:   ('sh_entsize', 8)
+