diff --git a/src/libANGLE/Program.cpp b/src/libANGLE/Program.cpp
index 86a1622..71b8264 100644
--- a/src/libANGLE/Program.cpp
+++ b/src/libANGLE/Program.cpp
@@ -1008,6 +1008,7 @@
     mState.mOutputVariables.clear();
     mState.mOutputLocations.clear();
     mState.mOutputVariableTypes.clear();
+    mState.mDrawBufferTypeMask.reset();
     mState.mActiveOutputVariables.reset();
     mState.mComputeShaderLocalSize.fill(1);
     mState.mSamplerBindings.clear();
@@ -2803,7 +2804,6 @@
     return merged;
 }
 
-
 void Program::linkOutputVariables(const Context *context)
 {
     Shader *fragmentShader = mState.mAttachedFragmentShader;
@@ -2811,6 +2811,7 @@
 
     ASSERT(mState.mOutputVariableTypes.empty());
     ASSERT(mState.mActiveOutputVariables.none());
+    ASSERT(mState.mDrawBufferTypeMask.none());
 
     // Gather output variable types
     for (const auto &outputVariable : fragmentShader->getActiveOutputVariables(context))
@@ -2838,6 +2839,7 @@
             ASSERT(location < mState.mActiveOutputVariables.size());
             mState.mActiveOutputVariables.set(location);
             mState.mOutputVariableTypes[location] = VariableComponentType(outputVariable.type);
+            mState.mDrawBufferTypeMask.setIndex(mState.mOutputVariableTypes[location], location);
         }
     }