diff --git a/src/util/trace.cpp b/src/util/trace.cpp
index 3410febd5..72984d808 100644
--- a/src/util/trace.cpp
+++ b/src/util/trace.cpp
@@ -23,8 +23,8 @@ Revision History:
 std::ofstream tout(".z3-trace"); 
 #endif
 
-bool g_enable_all_trace_tags = false;
-str_hashtable* g_enabled_trace_tags = 0;
+static bool g_enable_all_trace_tags = false;
+static str_hashtable* g_enabled_trace_tags = 0;
 
 static str_hashtable& get_enabled_trace_tags() {
     if (!g_enabled_trace_tags) {