diff --git a/lib/Target/ARM/Disassembler/ARMDisassemblerCore.cpp b/lib/Target/ARM/Disassembler/ARMDisassemblerCore.cpp
index 993ff7302f6..cc7f0d6e60c 100644
--- a/lib/Target/ARM/Disassembler/ARMDisassemblerCore.cpp
+++ b/lib/Target/ARM/Disassembler/ARMDisassemblerCore.cpp
@@ -82,8 +82,16 @@ const char *ARMUtils::OpcodeName(unsigned Opcode) {
 // FIXME: Auto-gened?
 static unsigned
 getRegisterEnum(BO B, unsigned RegClassID, unsigned RawRegister) {
-  // For this purpose, we can treat rGPR as if it were GPR.
-  if (RegClassID == ARM::rGPRRegClassID) RegClassID = ARM::GPRRegClassID;
+  if (RegClassID == ARM::rGPRRegClassID) {
+    // Check for The register numbers 13 and 15 that are not permitted for many
+    // Thumb register specifiers.
+    if (RawRegister == 13 || RawRegister == 15) {
+      B->SetErr(-1);
+      return 0;
+    }
+    // For this purpose, we can treat rGPR as if it were GPR.
+    RegClassID = ARM::GPRRegClassID;
+  }
 
   // See also decodeNEONRd(), decodeNEONRn(), decodeNEONRm().
   unsigned RegNum =
diff --git a/test/MC/Disassembler/ARM/thumb-printf.txt b/test/MC/Disassembler/ARM/thumb-printf.txt
index 6245b7cedc7..09f54abf824 100644
--- a/test/MC/Disassembler/ARM/thumb-printf.txt
+++ b/test/MC/Disassembler/ARM/thumb-printf.txt
@@ -26,7 +26,8 @@
 # CHECK-NEXT:	mov	r2, r5
 # CHECK-NEXT:	ldr	r3, [sp]
 # CHECK-NEXT:	bl	#-8390
-# CHECK-NEXT:	sub.w	sp, r7, #8
+# Data bytes (corresponds to an invalid instruction)
+# But not:	sub.w	sp, r7, #8
 # CHECK-NEXT:	pop.w	{r4, r5, r7, lr}
 # CHECK-NEXT:	add	sp, #16
 # CHECK-NEXT:	bx	lr
@@ -63,7 +64,7 @@
 0x2a	0x46
 0x00	0x9b
 0xfd	0xf7	0x9d	0xff
-0xa7	0xf1	0x08	0x0d
+# 0xa7	0xf1	0x08	0x0d
 0xbd	0xe8	0xb0	0x40
 0x04	0xb0
 0x70	0x47
diff --git a/test/MC/Disassembler/ARM/thumb-tests.txt b/test/MC/Disassembler/ARM/thumb-tests.txt
index fb53f5946cd..60520693929 100644
--- a/test/MC/Disassembler/ARM/thumb-tests.txt
+++ b/test/MC/Disassembler/ARM/thumb-tests.txt
@@ -42,8 +42,8 @@
 # CHECK:	ldrd	r0, r1, [r7, #64]!
 0xf7 0xe9 0x10 0x01
 
-# CHECK:	lsls.w	r0, pc, #1
-0x5f 0xea 0x4f 0x00
+# CHECK:	lsls.w	r0, r5, #1
+0x5f 0xea 0x45 0x00
 
 # CHECK:	mov	r11, r7
 0xbb 0x46