diff --git a/js/src/jit/BaselineCacheIRCompiler.cpp b/js/src/jit/BaselineCacheIRCompiler.cpp
index 7021433c3c..a376ffeb81 100644
--- a/js/src/jit/BaselineCacheIRCompiler.cpp
+++ b/js/src/jit/BaselineCacheIRCompiler.cpp
@@ -316,7 +316,7 @@ BaselineCacheIRCompiler::emitGuardSpecificAtom()
 
     // The pointers are not equal, so if the input string is also an atom it
     // must be a different string.
-    masm.branchTest32(Assembler::NonZero, Address(str, JSString::offsetOfFlags()),
+    masm.branchTest32(Assembler::Zero, Address(str, JSString::offsetOfFlags()),
                       Imm32(JSString::NON_ATOM_BIT), failure->label());
 
     // Check the length.
diff --git a/js/src/jit/IonCacheIRCompiler.cpp b/js/src/jit/IonCacheIRCompiler.cpp
index 3d49cf61dd..3c6c442c8f 100644
--- a/js/src/jit/IonCacheIRCompiler.cpp
+++ b/js/src/jit/IonCacheIRCompiler.cpp
@@ -684,7 +684,7 @@ IonCacheIRCompiler::emitGuardSpecificAtom()
 
     // The pointers are not equal, so if the input string is also an atom it
     // must be a different string.
-    masm.branchTest32(Assembler::NonZero, Address(str, JSString::offsetOfFlags()),
+    masm.branchTest32(Assembler::Zero, Address(str, JSString::offsetOfFlags()),
                       Imm32(JSString::NON_ATOM_BIT), failure->label());
 
     // Check the length.