diff --git a/src/gpu/GrContextThreadSafeProxy.cpp b/src/gpu/GrContextThreadSafeProxy.cpp
index 5b00895..7ad6fb3 100644
--- a/src/gpu/GrContextThreadSafeProxy.cpp
+++ b/src/gpu/GrContextThreadSafeProxy.cpp
@@ -64,11 +64,13 @@
         return SkSurfaceCharacterization(); // return an invalid characterization
     }
 
-    sampleCnt = this->caps()->getRenderTargetSampleCount(sampleCnt, grColorType, backendFormat);
-    if (!sampleCnt) {
+    if (!this->caps()->isFormatAsColorTypeRenderable(grColorType, backendFormat, sampleCnt)) {
         return SkSurfaceCharacterization(); // return an invalid characterization
     }
 
+    sampleCnt = this->caps()->getRenderTargetSampleCount(sampleCnt, backendFormat);
+    SkASSERT(sampleCnt);
+
     if (willUseGLFBO0 && isTextureable) {
         return SkSurfaceCharacterization(); // return an invalid characterization
     }