diff --git a/src/interpreter.c b/src/interpreter.c
index 008886f1c99c9..b9e282a0fba19 100644
--- a/src/interpreter.c
+++ b/src/interpreter.c
@@ -236,7 +236,8 @@ static jl_value_t *eval_value(jl_value_t *e, interpreter_state *s)
             }
         }
         else {
-            assert(0 && "malformed isdefined expression");
+            // QuoteNode or other implicitly quoted object
+            defined = 1;
         }
         return defined ? jl_true : jl_false;
     }
diff --git a/test/interpreter.jl b/test/interpreter.jl
index 0fea42e0aecdb..f3e9ee2bcae65 100644
--- a/test/interpreter.jl
+++ b/test/interpreter.jl
@@ -30,3 +30,11 @@ let p = Pipe(),
     wait(proc)
     close(p)
 end
+
+# interpreting Expr(:isdefined, ::QuoteNode)
+let code = """
+           @generated f() = Expr(:isdefined, QuoteNode(Float64))
+           f()
+           """
+    @test read(`$(Base.julia_cmd()) --startup-file=no --compile=min -E $code`, String) == "true\n"
+end