diff --git a/SPIRV/GlslangToSpv.cpp b/SPIRV/GlslangToSpv.cpp
index 8372dbb..a6c777c 100755
--- a/SPIRV/GlslangToSpv.cpp
+++ b/SPIRV/GlslangToSpv.cpp
@@ -524,10 +524,12 @@
     case glslang::EbvGlobalInvocationId:   return spv::BuiltInGlobalInvocationId;
 
     case glslang::EbvSubGroupSize:
+        builder.addExtension(spv::E_SPV_KHR_shader_ballot);
         builder.addCapability(spv::CapabilitySubgroupBallotKHR);
         return spv::BuiltInSubgroupSize;
 
     case glslang::EbvSubGroupInvocation:
+        builder.addExtension(spv::E_SPV_KHR_shader_ballot);
         builder.addCapability(spv::CapabilitySubgroupBallotKHR);
         return spv::BuiltInSubgroupLocalInvocationId;