diff --git a/src/node_credentials.cc b/src/node_credentials.cc
index 8a832b0e3efb3a..76088144950e49 100644
--- a/src/node_credentials.cc
+++ b/src/node_credentials.cc
@@ -49,7 +49,7 @@ namespace credentials {
 
 #if defined(__linux__)
 // Returns true if the current process only has the passed-in capability.
-bool HasOnly(int capability) {
+static bool HasOnly(int capability) {
   DCHECK(cap_valid(capability));
 
   struct __user_cap_data_struct cap_data[2];