diff --git a/ir/irfunction.cpp b/ir/irfunction.cpp
index 72374cc194..f3405a1c32 100644
--- a/ir/irfunction.cpp
+++ b/ir/irfunction.cpp
@@ -138,7 +138,7 @@ void ScopeStack::runCleanups(
     }
 
     // Insert the unconditional branch to the first cleanup block.
-    irs->ir->CreateBr(cleanupScopes.back().beginBlock);
+    irs->ir->CreateBr(cleanupScopes[sourceScope - 1].beginBlock);
 
     // Update all the control flow in the cleanups to make sure we end up where
     // we want.
@@ -353,6 +353,7 @@ llvm::BasicBlock* ScopeStack::emitLandingPad() {
         it != end; ++it
     ) {
         // Insert any cleanups in between the last catch we ran and this one.
+        assert(lastCleanup >= it->cleanupScope);
         if (lastCleanup > it->cleanupScope) {
             landingPad->setCleanup(true);
             llvm::BasicBlock* afterCleanupBB = llvm::BasicBlock::Create(
diff --git a/ir/irfunction.h b/ir/irfunction.h
index d176e7c33a..27ab0e60e4 100644
--- a/ir/irfunction.h
+++ b/ir/irfunction.h
@@ -322,7 +322,8 @@ private:
     ///
     std::vector<JumpTarget> continueTargets;
 
-    ///
+    /// cleanupScopes[i] contains the information to go from
+    /// currentCleanupScope() == i + 1 to currentCleanupScope() == i.
     std::vector<CleanupScope> cleanupScopes;
 
     ///
@@ -361,7 +362,9 @@ llvm::CallSite ScopeStack::callOrInvoke(llvm::Value* callee, const T &args,
     }
 
     if (currentLandingPads().empty()) {
-        // Have not encountered.
+        // Have not encountered any catches (for which we would push a scope) or
+        // calls to throwing functions (where we would have already executed
+        // this if) in this cleanup scope yet.
         currentLandingPads().push_back(0);
     }