diff --git a/compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/phaser/CompilerPhase.kt b/compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/phaser/CompilerPhase.kt
index 275ce8a2799..ecdfbfdd3b9 100644
--- a/compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/phaser/CompilerPhase.kt
+++ b/compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/phaser/CompilerPhase.kt
@@ -81,7 +81,10 @@ abstract class AbstractNamedPhaseWrapper<in Context : CommonBackendContext, Inpu
             return input as Output
         }
 
-        assert(phaserState.alreadyDone.containsAll(prerequisite))
+        assert(phaserState.alreadyDone.containsAll(prerequisite)) {
+            "Lowering $name: phases ${(prerequisite - phaserState.alreadyDone).map { it.name }} are required, but not satisfied"
+        }
+
         context.inVerbosePhase = this in phaseConfig.verbose
 
         runBefore(phaseConfig, context, input)