diff --git a/js/src/jit/IonAnalysis.cpp b/js/src/jit/IonAnalysis.cpp
index 816e0a17519..b2cfa2cef9e 100644
--- a/js/src/jit/IonAnalysis.cpp
+++ b/js/src/jit/IonAnalysis.cpp
@@ -3482,7 +3482,9 @@ MakeLoopContiguous(MIRGraph &graph, MBasicBlock *header, size_t numMarked)
     size_t headerId = header->id();
     size_t inLoopId = headerId;
     size_t notInLoopId = inLoopId + numMarked;
+    size_t numOSRDominated = 0;
     ReversePostorderIterator i = graph.rpoBegin(header);
+    MBasicBlock *osrBlock = graph.osrBlock();
     for (;;) {
         MBasicBlock *block = *i++;
         MOZ_ASSERT(block->id() >= header->id() && block->id() <= backedge->id(),
@@ -3495,6 +3497,15 @@ MakeLoopContiguous(MIRGraph &graph, MBasicBlock *header, size_t numMarked)
             // If we've reached the loop backedge, we're done!
             if (block == backedge)
                 break;
+        } else if (osrBlock && osrBlock->dominates(block)) {
+            // This block is not in the loop, but since it's dominated by the
+            // OSR entry, the block was probably in the loop before some
+            // folding. This probably means that the block has outgoing paths
+            // which re-enter the loop in the middle. And that, finally, means
+            // that we can't move this block to the end, since it could create a
+            // backwards branch to a block which is not the loop header.
+            block->setId(inLoopId++);
+            ++numOSRDominated;
         } else {
             // This block is not in the loop. Move it to the end.
             graph.moveBlockBefore(insertPt, block);
@@ -3502,8 +3513,11 @@ MakeLoopContiguous(MIRGraph &graph, MBasicBlock *header, size_t numMarked)
         }
     }
     MOZ_ASSERT(header->id() == headerId, "Loop header id changed");
-    MOZ_ASSERT(inLoopId == headerId + numMarked, "Wrong number of blocks kept in loop");
-    MOZ_ASSERT(notInLoopId == (insertIter != graph.rpoEnd() ? insertPt->id() : graph.numBlocks()),
+    MOZ_ASSERT(inLoopId == headerId + numMarked + numOSRDominated,
+               "Wrong number of blocks kept in loop");
+    MOZ_ASSERT(notInLoopId == (insertIter != graph.rpoEnd()
+                               ? insertPt->id()
+                               : graph.numBlocks()) - numOSRDominated,
                "Wrong number of blocks moved out of loop");
 }