diff --git a/lib/CodeGen/RegisterScavenging.cpp b/lib/CodeGen/RegisterScavenging.cpp
index cf90aba86b3..94680ed2992 100644
--- a/lib/CodeGen/RegisterScavenging.cpp
+++ b/lib/CodeGen/RegisterScavenging.cpp
@@ -100,11 +100,8 @@ void RegScavenger::enterBasicBlock(MachineBasicBlock *mbb) {
         CalleeSavedRegs.set(CSRegs[i]);
   }
 
-  // RS used within emit{Pro,Epi}logue()
-  if (mbb != MBB) {
-    MBB = mbb;
-    initRegState();
-  }
+  MBB = mbb;
+  initRegState();
 
   Tracking = false;
 }
diff --git a/test/CodeGen/Thumb2/2009-11-11-ScavengerAssert.ll b/test/CodeGen/Thumb2/2009-11-11-ScavengerAssert.ll
new file mode 100644
index 00000000000..16db037c18f
--- /dev/null
+++ b/test/CodeGen/Thumb2/2009-11-11-ScavengerAssert.ll
@@ -0,0 +1,85 @@
+; RUN: llc < %s -mtriplethumbv7-apple-darwin10
+
+%struct.OP = type { %struct.OP*, %struct.OP*, %struct.OP* ()*, i32, i16, i16, i8, i8 }
+%struct.SV = type { i8*, i32, i32 }
+
+declare arm_apcscc void @Perl_mg_set(%struct.SV*) nounwind
+
+define arm_apcscc %struct.OP* @Perl_pp_complement() nounwind {
+entry:
+  %0 = load %struct.SV** null, align 4            ; <%struct.SV*> [#uses=2]
+  br i1 undef, label %bb21, label %bb5
+
+bb5:                                              ; preds = %entry
+  br i1 undef, label %bb13, label %bb6
+
+bb6:                                              ; preds = %bb5
+  br i1 undef, label %bb8, label %bb7
+
+bb7:                                              ; preds = %bb6
+  %1 = getelementptr inbounds %struct.SV* %0, i32 0, i32 0 ; <i8**> [#uses=1]
+  %2 = load i8** %1, align 4                      ; <i8*> [#uses=1]
+  %3 = getelementptr inbounds i8* %2, i32 12      ; <i8*> [#uses=1]
+  %4 = bitcast i8* %3 to i32*                     ; <i32*> [#uses=1]
+  %5 = load i32* %4, align 4                      ; <i32> [#uses=1]
+  %storemerge5 = xor i32 %5, -1                   ; <i32> [#uses=1]
+  call arm_apcscc  void @Perl_sv_setiv(%struct.SV* undef, i32 %storemerge5) nounwind
+  %6 = getelementptr inbounds %struct.SV* undef, i32 0, i32 2 ; <i32*> [#uses=1]
+  %7 = load i32* %6, align 4                      ; <i32> [#uses=1]
+  %8 = and i32 %7, 16384                          ; <i32> [#uses=1]
+  %9 = icmp eq i32 %8, 0                          ; <i1> [#uses=1]
+  br i1 %9, label %bb12, label %bb11
+
+bb8:                                              ; preds = %bb6
+  unreachable
+
+bb11:                                             ; preds = %bb7
+  call arm_apcscc  void @Perl_mg_set(%struct.SV* undef) nounwind
+  br label %bb12
+
+bb12:                                             ; preds = %bb11, %bb7
+  store %struct.SV* undef, %struct.SV** null, align 4
+  br label %bb44
+
+bb13:                                             ; preds = %bb5
+  %10 = call arm_apcscc  i32 @Perl_sv_2uv(%struct.SV* %0) nounwind ; <i32> [#uses=0]
+  br i1 undef, label %bb.i, label %bb1.i
+
+bb.i:                                             ; preds = %bb13
+  call arm_apcscc  void @Perl_sv_setiv(%struct.SV* undef, i32 undef) nounwind
+  br label %Perl_sv_setuv.exit
+
+bb1.i:                                            ; preds = %bb13
+  br label %Perl_sv_setuv.exit
+
+Perl_sv_setuv.exit:                               ; preds = %bb1.i, %bb.i
+  %11 = getelementptr inbounds %struct.SV* undef, i32 0, i32 2 ; <i32*> [#uses=1]
+  %12 = load i32* %11, align 4                    ; <i32> [#uses=1]
+  %13 = and i32 %12, 16384                        ; <i32> [#uses=1]
+  %14 = icmp eq i32 %13, 0                        ; <i1> [#uses=1]
+  br i1 %14, label %bb20, label %bb19
+
+bb19:                                             ; preds = %Perl_sv_setuv.exit
+  call arm_apcscc  void @Perl_mg_set(%struct.SV* undef) nounwind
+  br label %bb20
+
+bb20:                                             ; preds = %bb19, %Perl_sv_setuv.exit
+  store %struct.SV* undef, %struct.SV** null, align 4
+  br label %bb44
+
+bb21:                                             ; preds = %entry
+  br i1 undef, label %bb23, label %bb22
+
+bb22:                                             ; preds = %bb21
+  unreachable
+
+bb23:                                             ; preds = %bb21
+  unreachable
+
+bb44:                                             ; preds = %bb20, %bb12
+  ret %struct.OP* undef
+}
+
+declare arm_apcscc void @Perl_sv_setiv(%struct.SV*, i32) nounwind
+
+declare arm_apcscc i32 @Perl_sv_2uv(%struct.SV*) nounwind