--- a/layout/style/nsCSSValue.cpp
+++ b/layout/style/nsCSSValue.cpp
@@ -868,17 +868,17 @@ nsCSSValue::GetCalcValue() const
     result.mLength = rootValue.GetFloatValue();
     result.mPercent = 0.0f;
     result.mHasPercent = false;
   } else {
     MOZ_ASSERT(rootValue.GetUnit() == eCSSUnit_Calc_Plus,
                "Calc unit should be eCSSUnit_Calc_Plus");
 
     const nsCSSValue::Array *calcPlusArray = rootValue.GetArrayValue();
-    MOZ_ASSERT(array->Count() == 2,
+    MOZ_ASSERT(calcPlusArray->Count() == 2,
                "eCSSUnit_Calc_Plus should have a 2-length array");
 
     const nsCSSValue& length = calcPlusArray->Item(0);
     const nsCSSValue& percent = calcPlusArray->Item(1);
     MOZ_ASSERT(length.GetUnit() == eCSSUnit_Pixel,
                "The first value should be eCSSUnit_Pixel");
     MOZ_ASSERT(percent.GetUnit() == eCSSUnit_Percent,
                "The first value should be eCSSUnit_Percent");