diff --git a/core/src/main/scala/wartremover/warts/StringPlusAny.scala b/core/src/main/scala/wartremover/warts/StringPlusAny.scala
index 44a61983..6a0dbc8a 100644
--- a/core/src/main/scala/wartremover/warts/StringPlusAny.scala
+++ b/core/src/main/scala/wartremover/warts/StringPlusAny.scala
@@ -6,6 +6,8 @@ object StringPlusAny extends WartTraverser {
     import u.universe._
 
     val Plus: TermName = "$plus"
+    val PredefName: TermName = "Predef"
+    val Any2StringAddName: TermName = "any2stringadd"
 
     def isString(t: Tree) = t.tpe <:< typeOf[String]
 
@@ -22,7 +24,18 @@ object StringPlusAny extends WartTraverser {
           // Ignore trees marked by SuppressWarnings
           case t if hasWartAnnotation(u)(t) =>
 
-          case t @ Apply(Select(lhs, Plus), List(rhs)) if isString(t) && (isString(lhs) ^ isStringExpression(rhs))
+          case Apply(Select(Select(_, PredefName), Any2StringAddName), _) =>
+            u.error(tree.pos, "Implicit conversion to string is disabled")
+            super.traverse(tree)
+          case TypeApply(Select(Select(_, PredefName), Any2StringAddName), _) =>
+            u.error(tree.pos, "Implicit conversion to string is disabled")
+            super.traverse(tree)
+
+          case Apply(Select(Literal(Constant(c)), Plus), _) if !c.isInstanceOf[String] =>
+            u.error(tree.pos, "Implicit conversion to string is disabled")
+            super.traverse(tree)
+
+          case t @ Apply(Select(lhs, Plus), List(rhs)) if isString(lhs) && !isStringExpression(rhs)
               && !isSynthetic(u)(t) =>
             u.error(tree.pos, "Implicit conversion to string is disabled")
             super.traverse(tree)
diff --git a/core/src/test/scala/wartremover/warts/StringPlusAnyTest.scala b/core/src/test/scala/wartremover/warts/StringPlusAnyTest.scala
index cdd85ca9..fd8f623e 100644
--- a/core/src/test/scala/wartremover/warts/StringPlusAnyTest.scala
+++ b/core/src/test/scala/wartremover/warts/StringPlusAnyTest.scala
@@ -9,11 +9,17 @@ class StringPlusAnyTest extends FunSuite with ResultAssertions {
   test("Implicit conversion to string is disabled") {
     val result = WartTestTraverser(StringPlusAny) {
       {} + "lol"
-      1 + "lol"
       "lol" + 1
       "" + (if (true) 5 else "")
     }
-    assertErrors(result)("Implicit conversion to string is disabled", 4)
+    assertErrors(result)("Implicit conversion to string is disabled", 3)
+  }
+
+  test("Primitive conversion to string is disabled") {
+    val result = WartTestTraverser(StringPlusAny) {
+      1 + "lol"
+    }
+    assertError(result)("Implicit conversion to string is disabled")
   }
 
   test("Non-string + usage is allowed") {
@@ -47,7 +53,7 @@ class StringPlusAnyTest extends FunSuite with ResultAssertions {
 
   test("custom-defined + is allowed") {
     val result = WartTestTraverser(StringPlusAny) {
-      class C { def +(s: String) = this }
+      class C { def +(s: String) = s }
       new C + "a"
     }
     assertEmpty(result)