diff --git a/src/compiler/scala/tools/nsc/transform/LambdaLift.scala b/src/compiler/scala/tools/nsc/transform/LambdaLift.scala
index c6a25bdd14e4..6420b40d08bf 100644
--- a/src/compiler/scala/tools/nsc/transform/LambdaLift.scala
+++ b/src/compiler/scala/tools/nsc/transform/LambdaLift.scala
@@ -178,7 +178,8 @@ abstract class LambdaLift extends InfoTransform {
             renamable += sym
             changedFreeVars = true
             debuglog(s"$sym is free in $enclosure")
-            if (sym.isVariable) sym setFlag CAPTURED
+            if (sym.isVariable && !sym.hasStableFlag) // write-once synthetic case vars are marked STABLE
+              sym setFlag CAPTURED
           }
           !enclosure.isClass
         }
diff --git a/src/compiler/scala/tools/nsc/transform/patmat/MatchOptimization.scala b/src/compiler/scala/tools/nsc/transform/patmat/MatchOptimization.scala
index ba25b21820f3..2fc39ea7c271 100644
--- a/src/compiler/scala/tools/nsc/transform/patmat/MatchOptimization.scala
+++ b/src/compiler/scala/tools/nsc/transform/patmat/MatchOptimization.scala
@@ -14,7 +14,7 @@ package scala.tools.nsc.transform.patmat
 
 import scala.language.postfixOps
 
-import scala.tools.nsc.symtab.Flags.MUTABLE
+import scala.tools.nsc.symtab.Flags.{MUTABLE, STABLE}
 import scala.collection.mutable
 import scala.reflect.internal.util.Position
 
@@ -149,7 +149,7 @@ trait MatchOptimization extends MatchTreeMaking with MatchAnalysis {
       lazy val localSubstitution        = Substitution(List(prevBinder), List(CODE.REF(nextBinder)))
       lazy val storedCond               = freshSym(selectorPos, BooleanTpe, "rc") setFlag MUTABLE
       lazy val treesToHoist: List[Tree] = {
-        nextBinder setFlag MUTABLE
+        nextBinder setFlag MUTABLE | STABLE // mark stable to tell lambalift not to capture these as the value will be assigned prior to capture and never reassigned.
         nextBinder.setPos(selectorPos)
         List(storedCond, nextBinder) map (b => ValDef(b, codegen.mkZero(b.info)))
       }
diff --git a/test/files/run/sd187.check b/test/files/run/sd187.check
index f88fbc292333..2257aa0f0ccd 100644
--- a/test/files/run/sd187.check
+++ b/test/files/run/sd187.check
@@ -7,7 +7,7 @@
     };
     [107]def commonSubPattern([124]x: [127]<type: [127]scala.Any>): [107]AnyVal = [205]{
       [205]<synthetic> var rc6: [205]Boolean = [205]false;
-      [205]<synthetic> var x3: [205]String = [205][205][205]null.asInstanceOf[[205]String];
+      [205]<synthetic> <stable> var x3: [205]String = [205][205][205]null.asInstanceOf[[205]String];
       [205]{
         [205]case <synthetic> val x1: [205]Any = [205]x;
         [205]case8(){