diff --git a/loopy/codegen/instruction.py b/loopy/codegen/instruction.py
index 383988863..f3b9793b3 100644
--- a/loopy/codegen/instruction.py
+++ b/loopy/codegen/instruction.py
@@ -114,6 +114,7 @@ def generate_assignment_instruction_code(codegen_state, insn):
     # {{{ vectorization handling
 
     if codegen_state.vectorization_info:
+        from loopy.symbolic import get_dependencies
         if insn.atomicity:
             raise UnvectorizableError("atomic operation")
 
@@ -134,6 +135,13 @@ def generate_assignment_instruction_code(codegen_state, insn):
             raise UnvectorizableError(
                     "LHS is vector, RHS is not vector, cannot assign")
 
+        if codegen_state.vectorization_info.iname in get_dependencies(
+                tuple(insn.predicates)):
+            raise NotImplementedError("https://github.com/inducer/loopy/issues/615")
+            raise UnvectorizableError(
+                    "Instruction contains a predicate depending on the vectorized"
+                    " loop.")
+
         is_vector = lhs_is_vector
 
         del lhs_is_vector