diff --git a/reactor/API/src/jetbrains/mps/logic/reactor/program/Handler.java b/reactor/API/src/jetbrains/mps/logic/reactor/program/Handler.java
index 8942af80..9bad4740 100644
--- a/reactor/API/src/jetbrains/mps/logic/reactor/program/Handler.java
+++ b/reactor/API/src/jetbrains/mps/logic/reactor/program/Handler.java
@@ -7,7 +7,7 @@ public abstract class Handler {
 
     public abstract String name();
 
-    public abstract ConstraintSymbol primarySymbol();
+    public abstract Iterable<ConstraintSymbol> primarySymbols();
 
     public abstract Iterable<Rule> rules();
 
diff --git a/reactor/Core/src/jetbrains/mps/logic/reactor/core/RuleIndex.kt b/reactor/Core/src/jetbrains/mps/logic/reactor/core/RuleIndex.kt
index b3b9e0a8..ca5d1dbb 100644
--- a/reactor/Core/src/jetbrains/mps/logic/reactor/core/RuleIndex.kt
+++ b/reactor/Core/src/jetbrains/mps/logic/reactor/core/RuleIndex.kt
@@ -33,35 +33,30 @@ class RuleIndex : Iterable<Rule> {
 
     fun byTag(tag: String): Rule? = tag2rule[tag]
 
-    fun forOccurrence(occ: ConstraintOccurrence): Iterable<Rule> {
-        val primary = primarySymbol2valueIndex.get(occ.constraint().symbol())?.select(occ) ?: emptyList()
-        val all = allSymbol2valueIndex.get(occ.constraint().symbol())?.select(occ) ?: emptyList()
-        return primary + all
-    }
+    fun forOccurrence(occ: ConstraintOccurrence): Iterable<Rule> =
+        primarySymbol2valueIndex.get(occ.constraint().symbol())?.select(occ) ?:
+            (allSymbol2valueIndex.get(occ.constraint().symbol())?.select(occ) ?: emptyList())
 
     override fun iterator(): Iterator<Rule> = tag2rule.values.iterator()
 
     private fun buildIndex(handlers: Iterable<Handler>) {
+        // first, init the primary symbols value index
+        handlers
+            .flatMap { h -> h.primarySymbols() }
+            .forEach { symbol -> primarySymbol2valueIndex.getOrPut(symbol) { ValueIndex(symbol) } }
+
         for (h in handlers) {
-            val primaryValueIdx = h.primarySymbol()?.let { symbol ->
-                allSymbol2valueIndex.getOrPut(symbol) { ValueIndex(symbol) }
-            }
+            val hPrimSyms = h.primarySymbols().toSet()
             for (r in h.rules()) {
-                for (c in r.headKept()) {
-                    if (c.symbol() == h.primarySymbol()) {
-                        primaryValueIdx?.update(r, c)
-
-                    } else if (h.primarySymbol() == null) {
-                        allSymbol2valueIndex.getOrPut(c.symbol()) { ValueIndex(c.symbol()) }.update(r, c)
+                for (c in (r.headKept() + r.headReplaced())) {
+                    val symbol = c.symbol()
+                    if (symbol in hPrimSyms) {
+                        primarySymbol2valueIndex[symbol]?.update(r, c)
                     }
-                }
-                for (c in r.headReplaced()) {
-                    if (c.symbol() == h.primarySymbol()) {
-                        primaryValueIdx?.update(r, c)
-
-                    } else if (h.primarySymbol() == null) {
-                        allSymbol2valueIndex.getOrPut(c.symbol()) { ValueIndex(c.symbol()) }.update(r, c)
+                    else if (hPrimSyms.isEmpty()) {
+                        allSymbol2valueIndex.getOrPut(symbol) { ValueIndex(symbol) }.update(r, c)
                     }
+                    // else ignore the constraint -- it's not meant to be processed by this handler, as it is not a primary
                 }
             }
         }
diff --git a/reactor/Test/src/program/MockProgram.kt b/reactor/Test/src/program/MockProgram.kt
index f0c4cd3d..11f8c426 100644
--- a/reactor/Test/src/program/MockProgram.kt
+++ b/reactor/Test/src/program/MockProgram.kt
@@ -27,7 +27,7 @@ class ProgramBuilder(val registry: ConstraintRegistry)  {
 
 }
 
-open class HandlerBuilder(val name: String, val primary: ConstraintSymbol?) {
+open class HandlerBuilder(val name: String, val primary: Iterable<ConstraintSymbol>) {
     val rules = ArrayList<Rule>()
 
     fun appendRule(rule: Rule) {
@@ -61,12 +61,12 @@ open class RuleBuilder(val tag: String) {
 
 class MockHandler(
     val name: String,
-    val primary: ConstraintSymbol?,
+    val primary: Iterable<ConstraintSymbol>,
     val rules: List<Rule>) : Handler() {
 
     override fun name(): String = name
 
-    override fun primarySymbol(): ConstraintSymbol? = primary
+    override fun primarySymbols(): Iterable<ConstraintSymbol> = primary
 
     override fun rules(): Iterable<Rule> = rules
 }
diff --git a/reactor/Test/test/RulesHelper.kt b/reactor/Test/test/RulesHelper.kt
index a0cf1e37..9414e75c 100644
--- a/reactor/Test/test/RulesHelper.kt
+++ b/reactor/Test/test/RulesHelper.kt
@@ -34,7 +34,7 @@ fun programWithRules(pb: ProgramBuilder, vararg ruleBuilders : Environment.() ->
 }
 
 private fun programWithRules(env: Environment, ruleBuilders: Array<out Environment.() -> Rule>): Builder {
-    return builder(env, arrayOf(handler("test", null, * ruleBuilders)))
+    return builder(env, arrayOf(handler("test", emptyList(), * ruleBuilders)))
 }
 
 fun programWithHandlers(vararg handlerBuilders : Environment.() -> Handler): Builder {
@@ -51,7 +51,7 @@ private fun builder(env: Environment, handlerBlocks: Array<out Environment.() ->
     return Builder(env, handlers)
 }
 
-fun handler(name: String, primary: ConstraintSymbol?, vararg ruleBlocks: Environment.() -> Rule): Environment.() -> Handler = {
+fun handler(name: String, primary: Iterable<ConstraintSymbol>, vararg ruleBlocks: Environment.() -> Rule): Environment.() -> Handler = {
     val hb = HandlerBuilder(name, primary)
     for (block in ruleBlocks) {
         hb.appendRule(this.block())
diff --git a/reactor/Test/test/TestMatcher.kt b/reactor/Test/test/TestMatcher.kt
index ecc977e7..baac1496 100644
--- a/reactor/Test/test/TestMatcher.kt
+++ b/reactor/Test/test/TestMatcher.kt
@@ -184,13 +184,13 @@ class TestMatcher {
     @Test
     fun multipleHandlers() {
         programWithHandlers(
-            handler("handler1", ConstraintSymbol("foo", 0),
+            handler("handler1", listOf(ConstraintSymbol("foo", 0)),
                 rule("main1",
                     headKept(
                         constraint("foo")
                     ))
                 ),
-            handler("handler2", ConstraintSymbol("bar", 0),
+            handler("handler2", listOf(ConstraintSymbol("bar", 0)),
                 rule("main2",
                     headKept(
                         constraint("bar")
diff --git a/reactor/Test/test/TestProgramBuilder.kt b/reactor/Test/test/TestProgramBuilder.kt
index 2f1eb257..fb8fb878 100644
--- a/reactor/Test/test/TestProgramBuilder.kt
+++ b/reactor/Test/test/TestProgramBuilder.kt
@@ -39,7 +39,7 @@ class TestProgramBuilder {
                     constraint("bar")
                 ))).run {
 
-            programBuilder.addHandler(MockHandler("test", null, rules))
+            programBuilder.addHandler(MockHandler("test", emptyList(), rules))
             assertEquals(programBuilder.program("test").rules().count(), 1)
             assertEquals(programBuilder.program("test").rules().count(), 1)
         }
@@ -66,7 +66,7 @@ class TestProgramBuilder {
                     constraint("blah")
                 ))).run {
 
-            programBuilder.addHandler(MockHandler("test", null, rules))
+            programBuilder.addHandler(MockHandler("test", emptyList(), rules))
             assertEquals(programBuilder.program("test").rules().count(), 2)
         }
     }
@@ -82,7 +82,7 @@ class TestProgramBuilder {
                     constraint("bar", "1")
                 ))).run {
 
-            programBuilder.addHandler(MockHandler("test", null, rules))
+            programBuilder.addHandler(MockHandler("test", emptyList(), rules))
         }
     }
 }