--- a/js/src/jit/BaselineIC.cpp
+++ b/js/src/jit/BaselineIC.cpp
@@ -4760,16 +4760,20 @@ CanOptimizeDenseOrUnboxedArraySetElem(JS
 
     *isAddingCaseOut = false;
     *protoDepthOut = 0;
 
     // Some initial sanity checks.
     if (initLength < oldInitLength || capacity < oldCapacity)
         return false;
 
+    // Unboxed arrays need to be able to emit floating point code.
+    if (obj->is<UnboxedArrayObject>() && !obj->runtimeFromMainThread()->jitSupportsFloatingPoint)
+        return false;
+
     Shape* shape = obj->maybeShape();
 
     // Cannot optimize if the shape changed.
     if (oldShape != shape)
         return false;
 
     // Cannot optimize if the capacity changed.
     if (oldCapacity != capacity)