diff --git a/loopy/codegen/instruction.py b/loopy/codegen/instruction.py
index 3ef7c8f6ad6c8af09dd01bf9e1341179d2be0be7..e590502fb5813af0a820d45228de8e11c35a46c8 100644
--- a/loopy/codegen/instruction.py
+++ b/loopy/codegen/instruction.py
@@ -200,7 +200,7 @@ def generate_assignment_instruction_code(codegen_state, insn):
                     "(%s).y" % lhs_code])
 
         if printf_args:
-            printf_args_str = ", " + ", ".join(printf_args)
+            printf_args_str = ", " + ", ".join(str(v) for v in printf_args)
         else:
             printf_args_str = ""