diff --git a/clang-tools-extra/include-cleaner/lib/WalkAST.cpp b/clang-tools-extra/include-cleaner/lib/WalkAST.cpp
--- a/clang-tools-extra/include-cleaner/lib/WalkAST.cpp
+++ b/clang-tools-extra/include-cleaner/lib/WalkAST.cpp
@@ -82,10 +82,6 @@
     for (const auto *Shadow : UD->shadows()) {
       auto *TD = Shadow->getTargetDecl();
       auto IsUsed = TD->isUsed() || TD->isReferenced();
-      // We ignore unused overloads inside implementation files, as the ones in
-      // headers might still be used by the dependents of the header.
-      if (!IsUsed && !IsHeader)
-        continue;
       report(UD->getLocation(), TD,
              IsUsed ? RefType::Explicit : RefType::Ambiguous);
     }
diff --git a/clang-tools-extra/include-cleaner/unittests/WalkASTTest.cpp b/clang-tools-extra/include-cleaner/unittests/WalkASTTest.cpp
--- a/clang-tools-extra/include-cleaner/unittests/WalkASTTest.cpp
+++ b/clang-tools-extra/include-cleaner/unittests/WalkASTTest.cpp
@@ -88,12 +88,10 @@
     auto RTStr = llvm::to_string(RT);
     for (auto Expected : Target.points(RTStr))
       if (!llvm::is_contained(ReferencedOffsets[RT], Expected))
-        DiagnosePoint("location not marked used with type " + RTStr,
-                      Expected);
+        DiagnosePoint("location not marked used with type " + RTStr, Expected);
     for (auto Actual : ReferencedOffsets[RT])
       if (!llvm::is_contained(Target.points(RTStr), Actual))
-        DiagnosePoint("location unexpectedly used with type " + RTStr,
-                      Actual);
+        DiagnosePoint("location unexpectedly used with type " + RTStr, Actual);
   }
 
   // If there were any differences, we print the entire referencing code once.
@@ -129,19 +127,39 @@
 }
 
 TEST(WalkAST, Using) {
-  // Make sure we ignore unused overloads.
+  // We should report unused overloads as ambiguous.
   testWalk(R"cpp(
     namespace ns {
-      void $explicit^x(); void x(int); void x(char);
+      void $explicit^x(); void $ambiguous^x(int); void $ambiguous^x(char);
     })cpp",
            "using ns::^x; void foo() { x(); }");
-  // We should report unused overloads if main file is a header.
   testWalk(R"cpp(
     namespace ns {
       void $ambiguous^x(); void $ambiguous^x(int); void $ambiguous^x(char);
     })cpp",
            "// c++-header\n using ns::^x;");
+  testWalk(R"cpp(
+    namespace ns {
+      void $ambiguous^x(); void $ambiguous^x(int); void $ambiguous^x(char);
+    })cpp",
+           "using ns::^x;");
   testWalk("namespace ns { struct S; } using ns::$explicit^S;", "^S *s;");
+
+  // We should report references to templates as ambiguous.
+  testWalk(R"cpp(
+    namespace ns {
+      template<class T>
+      class $ambiguous^Y {};
+    }
+    )cpp",
+           "using ns::^Y; Y<int> x;");
+  testWalk(R"cpp(
+    namespace ns {
+      template<class T>
+      class $ambiguous^Y {};
+    }
+    )cpp",
+           "using ns::^Y;");
 }
 
 TEST(WalkAST, Namespaces) {