diff --git a/src/gpu/GrGLProgram.cpp b/src/gpu/GrGLProgram.cpp
index 28e4fc1..9fe195c 100644
--- a/src/gpu/GrGLProgram.cpp
+++ b/src/gpu/GrGLProgram.cpp
@@ -1709,7 +1709,7 @@
 
     };
 
-    const char* swizzle;
+    const char* swizzle = "";
     switch (desc.fSwizzle) {
         case StageDesc::kAlphaSmear_Swizzle:
             swizzle = ".aaaa";
@@ -1720,6 +1720,8 @@
         case StageDesc::kNone_Swizzle:
             swizzle = "";
             break;
+        default:
+            GrCrash("Swizzle descriptor didn't match any expected value");
     }
 
     GrStringBuilder modulate;