diff --git a/extensions.cpp b/extensions.cpp
index ffeb059..fa68789 100644
--- a/extensions.cpp
+++ b/extensions.cpp
@@ -1,5 +1,9 @@
 #include "extensions.hpp"
 
+// The 'extensions_test' testcase needs to define these itself.
+// Skip over the definition to avoid duplicate symbol definitions.
+#ifndef TESTCASE_extensions_test
+
 namespace phosphor
 {
 namespace logging
@@ -14,3 +18,5 @@
 
 } // namespace logging
 } // namespace phosphor
+
+#endif