diff --git a/js/src/ion/BytecodeAnalysis.h b/js/src/ion/BytecodeAnalysis.h
index e89bf5b2591..68dedcbd613 100644
--- a/js/src/ion/BytecodeAnalysis.h
+++ b/js/src/ion/BytecodeAnalysis.h
@@ -40,7 +40,7 @@ class BytecodeAnalysis
     Vector<BytecodeInfo, 0, IonAllocPolicy> infos_;
 
   public:
-    BytecodeAnalysis(JSScript *script);
+    explicit BytecodeAnalysis(JSScript *script);
 
     bool init();