diff --git a/test/unit/StringValueTest.h b/test/unit/StringValueTest.h
index 2943353315..a8e31f4fd3 100644
--- a/test/unit/StringValueTest.h
+++ b/test/unit/StringValueTest.h
@@ -6,7 +6,7 @@ namespace ntimpl {
 
 class StringValueTest : public ::testing::Test {
  public:
-  NT_String& ToNT(StringValue& v) { return v; }
+  static NT_String& ToNT(StringValue& v) { return v; }
 };
 
 }  // namespace ntimpl
diff --git a/test/unit/ValueTest.h b/test/unit/ValueTest.h
index abe49a28a4..105e3ed33d 100644
--- a/test/unit/ValueTest.h
+++ b/test/unit/ValueTest.h
@@ -6,7 +6,7 @@ namespace ntimpl {
 
 class ValueTest : public ::testing::Test {
  public:
-  NT_Value& ToNT(Value& v) { return v; }
+  static NT_Value& ToNT(Value& v) { return v; }
 };
 
 }  // namespace ntimpl